bluuebunny/crossref_metadata_2025 huggingface dataset:
Wall Pressure Correlations in Turbulent Airflow
Authors: Tack D. H. , Smith M. W. , Lambert R. F.
Published: September 2005

The correlation properties of turbulent wall pressure fluctuations are investigated experimentally with a view toward developing an adequate phenomenological model of the pressure correlation function for use in engineering calculations. It was found that both mean eddy sizes and mean eddy lifetimes determined by averaging over broad frequency bands did not contain sufficient information to accurately describe the high frequency end of the turbulent power spectrum. Thus, such gross quantities are of somewhat limited utility in detailed analysis, for instance, in predicting response of multimodal mechanical systems driven by flowing turbulence. However, by measuring eddy sizes and lifetimes over narrow frequency bands it appears possible to construct mathematical models for the turbulent pressure correlations which are successful in predicting the turbulent power spectrum over the frequency band of interest which could include the entire spectrum. In addition, measurements of rms pressure and space-time correlations are presented which supplement the data obtained by W. W. Willmarth [NASA Memo. 3-17-59 W (1959)] [or a somewhat higher reach range.
Some Basic Considerations in the Analysis of Intonation
Authors: Lehiste Ilse , Peterson Gordon E.
Published: September 2005

This paper considers some basic problems inherent in the instrumental analysis of intonation. The problems are illustrated by a detailed analysis of one intonation contour in American English. The material studied consisted of two sets of data. The first set involved 1263 sentences recorded by one speaker with determined stress and pitch patterns. The sentences consisted of 1263 CNC words produced in an identical frame, with primary stress and the peak of the intonation contour occurring on the CNC word in the frame. The second set of frame sentences involved a subset of 70 minimally different words, uttered by five different speakers of the same general dialect. The fundamental frequency values for the various levels of the intonation contour were measured from narrow-band sound spectrograms and the measurements were correlated with the segmental phonetic structure of the sentences in which the intonation contour was produced. The intrinsic fundamental frequencies of the various syllable nuclei and the influence of preceding and following consonants are described. The relationships among successive intonation levels are discussed.
Two Multivariate Statistical Computer Programs and Their Application to the Vowel Recognition Problem
Authors: Welch Peter D. , Wimpress Richard S.
Published: September 2005

This paper describes two IBM 704 EDPM programs which were written to aid in the development of mechanical speech recognition devices. Both are based upon multivariate statistical techniques. It further describes the application of the two programs to the problem of vowel recognition using fundamental frequency and formant information.
Mode Coupling Occurring in the Propagation of Elastic Pulses in Wires
Authors: Meitzler Allen H.
Published: September 2005

The propagation of elastic pulses in wires of circular cross section has been studied for conditions in which pulses having carrier frequencies ranging from 0.5 to 4.0 Mc were transmitted in wires having diameters between 0.1 and 0.2 cm. The pulses used in the experiments were shaped to have relatively narrow frequency spectra. At certain frequencies, herein called critical frequencies, pulses propagating in certain modes were observed to undergo pronounced distortion in which the peak amplitude of an affected pulse was reduced and the duration of the pulse was increased many times its original length. This pulse distortion associated with the presence of critical frequencies is shown to be caused by coupling between two modes of propagation. In agreement with predictions of the general theory of mode coupling, the critical frequencies are frequencies at which two modes of propagation have the same phase velocity.
Long-Range Sound Propagation in the Deep Ocean
Authors: Hale F. E.
Published: September 2005

The high intensity and low distortion of underwater acoustic signals propagated to convergence zones justifies a comprehensive description and an effort toward better organization of pertinent and related information. Convergence zones are the result of SOFAR Channel propagation from shallow sources to shallow receivers. The acoustic paths are analogous to those of skip-wave radio transmission. Although only illusive references exist in the open literature, there have been experiments showing as many as thirteen well-formed zones spaced over a 400 mile range interval. The propagation is quantitatively predictable, and quite stable. Convergence of acoustic energy along caustics results in losses smaller by about 20 db than those encountered in a free field.
Information Conveyed by Vowels
Authors: Ladefoged Peter , Broadbent D. E.
Published: September 2005

Most speech sounds may be said to convey three kinds of information: linguistic information which enables the listener to identify the words that are being used; socio-linguistic information, which enables him to appreciate something about the background of the speaker; and personal information which helps to identify the speaker. An experiment has been carried out which shows that the linguistic information conveyed by a vowel sound does not depend on the absolute values of its formant frequencies, but on the relationship between the formant frequencies for that vowel and the formant frequencies of other vowels pronounced by that speaker. Six versions of the sentence Please say what this word is were synthesized on a Parametric Artificial Talking device. Four test words of the form b-(vowel)-t were also synthesized. It is shown that the identification of the test word depends on the formant structure of the introductory sentence. Some psychological implications of this experiment are discussed, and hypotheses are put forward concerning the ways in which all three kinds of information are conveyed by vowels.
Acoustic Mapping within the Heart
Authors: Wallace John D. , Brown James R. , Lewis David H. , Deitz George W.
Published: September 2005

A cylindrical barium titanate element has been placed at the distal end of a specially designed catheter and used in studies of the heart sounds of dogs and humans. Heart sounds have been recorded with the element located in the four chambers of the heart as well as in the great vessels leading from the heart. X-ray photographs monitored the location of the catheter tip in each case. The sounds have been recorded on tape and simultaneously on a photographic galvanometer recorder, all studies were continuously monitored by electrocardiogram. Sound spectrographic analysis of the several sounds was made and analyzed.
On the Interpretation of Certain Sound Spectra of Musical Instruments
Authors: Young Robert W. , Dunn H. K.
Published: September 2005

The problem of computing sound power from measurements of average rectified sound pressure is reviewed, particularly in relation to “Absolute Amplitudes and Spectra of Certain Musical Instruments and Orchestras” published by Sivian, Dunn, and White in 1931. Experimental data on the distribution of instantaneous pressure amplitudes of music in a wide band and relations between rms and average pressure in octave and half-octave bands for speech are introduced; these data suggest, for example, that in a half-octave band in the vicinity of 1000 cps the rms sound-pressure level during a 15-sec interval of music exceeds the average pressure level by 9 db. Means are described for converting the old data based on “pressure per cycle” to a form that would be obtained with the modern octave band analyzer and sound level meter. In place of the steeply sloping spectra suggested by the original figures, the two kinds of corrections lead to an average sound power spectrum, for the 15-piece orchestra, having a broad peak between 100 and 4000 cps.
Acoustic Torques and Forces on Disks
Authors: Keller Joseph B.
Published: September 2005

The time-average forces and torques exerted by a plane sound wave upon fixed rigid disks of various shapes are calculated. Results are given for disks bounded by smooth closed convex curves. These results are then specialized to ellipses and circles. Results are also given for infinitely long thin strips. The results are all valid for ka large, where k = 2π/λ, λ being the wavelength and a being a typical dimension of the disk. The oscillatory behavior of the torque as a function of ka and the occurrence of numerous equilibrium positions are interesting consequences of these calculations.
Comparison Analysis on Four Directional Receiver Correlators
Authors: Jacobson M. J. , Talham R. J.
Published: September 2005

Four correlation systems are studied which make use of two pressure-gradient receivers having first-order cosine directional characteristics. The systems differ in the methods of steering both the receivers and the receiver baseline. The steering may be accomplished by rotation or by the insertion of appropriate time delays. The mean, variance, and output signal-noise ratio are computed for each system when a distant localized signal source is present in both circular and spherical noise fields. In addition, the directive properties of the mean outputs are examined. For a signal with rectangular power spectrum, the main lobe widths of the mean outputs are found, the behavior of the means in the neighborhood of source direction is examined, and an investigation is made of the mean output level for steering directions removed from source direction.
Subjective Evaluation of Musical Scale Temperament in Pianos
Authors: Martin D. W. , Ward W. D.
Published: September 2005

It is known that standard procedures used by piano tuners result in a “stretched” scale (i.e., upper tones higher and lower tones lower than the equally tempered scale). Although there was anecdotal evidence of the desirability of this stretch (largely natural consequence of tuning by beats) it had not been formally demonstrated. Therefore recorded tonal and chordal sequences from a small upright piano, tuned to a typical empirical stretched scale by means of a visual device, were compared with similar sequences from the same piano (1) tuned to strict equal temperament (again by means of the visual device), and (2) tuned by a factory “fine tuner” (by the conventional auditory method). Strict equal temperament was unequivocally rejected both by musically oriented research engineers and by music students. Sequences covering the entire piano scale gave the most pronounced preferences.
On the Origin of the Ultrasonic Absorption in Liquids. III
Authors: Herzfeld Karl F.
Published: September 2005

In “Kneser” liquids the mechanism of excess ultrasonic absorption is the slow exchange of energy between internal and external degrees of freedom, just as in gases. Eight such liquids are selected; in two the relaxation time in the liquid is known from measurements, in the others it is calculated from low-frequency absorption. In comparing the relaxation time for the liquids with that in the vapors of the same substances, the latter is found to be 100 to 600 times that in the liquid. This is related to the ratio of the collision times.
Ultrasonic Doppler Method for the Inspection of Cardiac Functions
Authors: Satomura Shigeo
Published: September 2005

When the continuous ultrasonic wave is sent forth towards the heart from the surface of the chest wall, the cardiac motion causes the Doppler effect upon the partial wave reflected from it. Therefore, an apparatus suitably constructed for sending and receiving ultrasounds is quite useful for the investigation of the movements of theatrium, ventricle, or valves, etc., through the analysis of the particular Doppler signals developed from the motion of the respective part.

The author developed a method for the inspection of cardiac functions by recording these Doppler signals simultaneously with the electro- and phonocardiographs the oscillograph paper. This method made it possible not only to obtain direct informations for the valvular movement which could not have been ascertained up to present, but also to examine the transitional aspects of the myocardial excitation which is utterly uudetectable by the electrocardiograph alone.
Reflection on a Rough Surface from an Acoustic Point Source
Authors: Biot M. A.
Published: September 2005

A simple solution is developed for the reflected waves on a rough surface from a simple harmonic point source. It is assumed that the roughness is represented by a distribution of hemispherical bosses whose size and mutual distance are small relative to the wavelength. It is shown that under these conditions the effect of the roughness is equivalent to a boundary condition for the wave equation. This boundary condition embodies the surface polarization and the mutual interaction of the bosses. If the generating source lies above the reflecting surface the reflected wave is found to be equivalent to that originating from concentrated and distributed image sources on a line situated below the specular image with a magnitude decreasing exponentially with depth. The case of vanishingly small roughness is discussed along with the field intensity at large distance and grazing incidence. The effect of fluid viscosity is also evaluated.
On Correlating the Loss Factors of Cylindrical and Spherical Resonators
Authors: Edmonds P. D.
Published: September 2005

Theoretical results are presented which relate the Q factors (internal friction) of solid resonators to two loss parameters λi and μi. The latter are assumed to be characteristic of the energy loss in the homogeneous, isotropic material constituting the resonators. Derivations start from the appropriate frequency—or velocity dispersion—equation in which complex elastic constants, λr+jλi and μr+jμi, are substituted. The following cases are treated: torsional, fundamental longitudinal and fundamental bending modes of solid cylinders, and radial modes of solid and hollow spheres. Deviations from constancy of Q are found in regions where velocity dispersion occurs. Computed results are tabulated which show the dependence of Qμ, upon λ1/μ1 (range 0.1–10) and the propagation factor τ (range 0–5 for cylinders); these apply to duralumin. Similar computations are used to interpret experimental results on polystyrene reported by Biesterfeldt, Lange, and Skudrzyk (see reference 22 in text), and an inconsistency is found in the values of λi calculated from the fundamental longitudinal and the fundamental bending modes of rods.
Vibrations of a Monoclinic Crystal Plate
Authors: Newman E. G. , Mindlin R. D.
Published: September 2005

There is described, in this paper, a detailed study of Ekstein's solution of the equations of elasticity for the case of the coupled vibrational modes of an infinite, monoclinic, crystal plate with traction-free faces. It is shown how the spectrum of frequencies and the character of the modes may be deduced by tracing the development of coupling from a simple solution in which the modes are uncoupled and by taking into account the asymptotic behavior at long and short wavelengths and high and low frequencies. The results of computations are given for the AT cut of quartz. The purpose of the investigation is to obtain some of the qualitative and quantitative information which is needed for the formulation of approximate equations of motion which may be solved for plates of finite dimensions.
Field of a Spatially Extended Moving Sound Source
Authors: Oestreicher Hans L.
Published: September 2005

The rigorous determination of the field of a spatially extended sound source moving with subsonic speed in a viscous compressible gas is formulated as an initial-boundary value problem of a system of linear partial differential equations. This system reduces to a single equation of the second order with variable coefficients if the medium is a perfect gas and the motion of the gas around the source a potential flow. For steady motions and harmonic sources the equation becomes elliptic if time is eliminated.

Generalizations of Green's identity and Helmholtz's formula for this partial differential equation allow the representation of the sound field as a series of generalized multipoles. The field of a sufficiently small source of arbitrary shape with boundary conditions appropriate for the acoustic case and its relation to the concept of a moving simple source, dipole, etc., is investigated.
Factors that Determine the Equivalent Noise Pressure, Free-Field Voltage Response, and Efficiency of a Transducer at Low Frequencies
Authors: Kendig Paul M.
Published: September 2005

The physical properties and dimensions that determine the equivalent noise pressures of several different shapes of piezoelectric transducers are examined. Expressions for the equivalent noise pressure, free-field voltage response, and electroacoustical efficiency at low frequencies—those frequencies for which the free-field voltage response is flat—are obtained in terms of generally known or easily measured parameters. The results indicate that at low frequencies a well designed hydrophone should have an equivalent noise pressure well below zero sea-state ambient. It is emphasized that the free-field voltage response is not an indication of the ability of a hydrophone to measure low-level signals, but that either the efficiency or the equivalent noise pressure is an essential indication of this ability.
Flow Resistance of Fibrous Materials
Authors: Bies David A. , Franken Peter A.
Published: September 2005

An empirical relationship is developed for the flow resistance of a variety of fibrous materials.
Acoustic Irritation Threshold of Peking Ducks and Other Domestic and Wild Fowl
Authors: Thiessen G. J. , Shaw E. A. G. , Harris R. D. , Gollop J. B. , Webster H. R.
Published: September 2005

When exposed to sounds of sufficient intensity Peking ducks respond in a characteristic manner combining head shaking and tail twitching. The response rate (number of responses per unit-time) increases with intensity up to a certain level, but falls with further increase in intensity. There is no response at intensities lower than a certain critical value which may therefore be described as the irritation threshold. Prolonged exposure to sound leads to a more or less exponential drop in response rate but recovery is rapid during rest periods. Measurements on about thirty ducks indicate that the threshold has a broad minimum at about 500 cps and the average value at this frequency is about 70 db [all sound pressure levels are given with respect to 0.0002 d/cm2] with a range of 65–85 db. There is some indication that the threshold is slightly lower for warble tones. At 15 and 18 kc no consistent responses have been obtained up to 115 and 120 db, respectively. Similar experiments with chickens and geese showed fewer responses and hence much less accurate results. It has also been shown that hungry Peking ducks are greatly discouraged from taking food placed in a low-frequency sound field at 100 db intensity.
Note on the Possible Use of Ultrasonic Pulse Compression by Bats
Authors: Strother G. K.
Published: September 2005

The analogy between echo-location techniques used by bats and those used by radar is extended to the relatively new pulse compression radar technique. The hypothesis that the hearing mechanism of the bat contains a frequency-dependent time delay network permits explanation of most of the anamolies associated with their behavior, including echo location by pulse, which overlap in space.
Further Observation on Pitch Associated with a Time Difference between Two Pulse Trains
Authors: Thurlow W. R.
Published: September 2005

Changing the time separation between two trains of filtered pulses, each at the same basic repetition rate, makes it evident that there is a pitch which is correlated with the magnitude of the time separation. When both trains of pulses are at 30 db sensation level, decreasing the intensity of one train of pulses by 10 db results in a noticeable asymmetry in the production of the “time-difference” pitches. That is, the “time-difference” pitches are much stronger when the pulses of the less intense train are in the second half of the interval between the pulses of the more intense train. No differences in spectra of the stimuli have been found which could explain this asymmetry.
Some Impedance Measurements on Normal and Pathological Ears
Authors: Zwislocki J.
Published: September 2005

The acoustic method of impedance measurement at the eardrum, described in the preceding paper, has been improved and applied to the investigation of the effect of some pathological changes in the middle ear on the measured impedance. The investigation shows that the otosclerosis and the interruption of the ossicular chain can be easily detected by means of the impedance measurement. An electrical and mathematical model of the dynamics of the middle ear is developed.
Diffraction Patterns Produced by Finite Amplitude Waves
Authors: Breazcale M. A. , Hiedemann E. A.
Published: September 2005

Pictures are given which illustrate in detail the optical effects produced by ultrasonic waves of finite amplitude in liquids. These effects can be used for the analysis of the wave form.
Utilization of Magnetostrictive Materials in Generating Intense Sound
Authors: Whymark R. R.
Published: September 2005

The intense sound output at resonance in a laminated nickel bar is calculated from static measurements of the relationship of the free magnetostrictive strain to the intrinsic induction. The limitations of the linear theory are avoided by determining the dynamic magnetostrictive stress which is taken to be the motivating influence of the mechanical vibrations. The dynamic magnetostrictive stress is obtained by graphical methods that are not limited to small excitation amplitudes, as is the case in the linear theory. Simple relationships of the dynamic magnetostrictive stress to the impedances of the transducer load system enable the sound output to be determined from the calculated magnitudes of the magnetostrictive stress. The calculated sound output is compared with the sound output measured on a laminated bar of annealed nickel, resonating longitudinally at 20 kcps, and coupled to an acoustic load consisting of a half-wavelength stub of highly dissipative cast iron. The sound energy delivered to the load is measured by a flow calorimeter, and mechanical transformers which are either solid exponential horns or stepped stubs are used to change the acoustic load to maximize the load power. The calculated sound outputs agree to within ±10% with the sound outputs measured calorimetrically. The measured maximum of the sound intensity is 167 w/cm2, while calculations show that 492 w/cm2 ultimately can be generated with the annealed nickel. Estimated intensities for a more freely mounted specimen are in excess of 1 kw/cm2.
Effects of Ambient Noise on Speaker Intelligibility for Words and Phrases
Authors: Dreher John J. , O'Neill John
Published: September 2005

The Lombard, or voice reflex, effect results in speech with characteristics different from those of speech that is normally produced. This change of characteristics can be demonstrated as an effective way to combat noise interference during reception. It also demonstrates the advisability of control of the production of speech by the speaker himself, in addition to that offered by equipment, during audiological evaluations.

Fifteen naive speakers read words and sentences while noise was being delivered to their headsets. There were five noise conditions. Their speech was recorded, with the noise being kept out of the recording channel, and then limited. Noise was then added to the recording in such a way as to produce a constant speech-to-noise ratio. The result was played to 200 American listeners. Results indicate that at a constant speech-to-noise ratio of reception speech produced by a talker with masking noise in his cars becomes more intelligible as the masking level rises to a given value. The change in intelligibility throughout the range investigated suggests an application to audiological testing as well as a device for use in voice communication.
Ultrasonic Attenuation in Water Containing Brine Shrimp in Suspension
Authors: Gruber George J. , Meister Robert
Published: September 2005

A study is made to determine the frequency and concentration dependence of the ultrasonic attenuation in aqueous suspensions of hatched and unhatched brine shrimp in the frequency range 1–45 Mc. In both types of suspensions a linear relationship is found to exist between the excess attenuation and concentration at each frequency. The attenuation caused by hatched brine shrimp is found to be the same when the organisms are either living or dead.

For both types of suspensions the major cause of the excess attenuation is attributed to a scattering mechanism. Over the range of frequencies studied, while the excess attenuation in a hatched brine shrimp suspension varies as the 1.35 power of frequency, the attenuation caused by unhatched brine shrimp exhibits a maximum. The fact that the unhatched brine shrimp can be considered as small spherical particles allows calculation of the scattering loss, which, when subtracted from the measured values, results in a resonance type loss. The measured loss maximum associated with this resonance occurs at a frequency coincident with the principle mode of oscillation calculated assuming the eggs to be spherical cavity oscillators. A simple theory of geometric scattering from unhatched brine shrimp gives attenuation values which agree exactly with those measured above 20 Mc.
Optical Measurement of Ultrasonic Fields
Authors: Weeks Richard F.
Published: September 2005

An apparatus is described which facilitates the measurement of ultrasonic fields within transparent solids. This optical system makes use of the birefringence produced within the solid by the passage of an ultrasonic wave. The interaction of light with ultrasonic fields is discussed and expressions derived for the modulation of light by both transverse and longitudinal ultrasonic waves. Various detection systems are discussed and the reasons for the choice of a system, making use of a wide slit in conjunction with a pulsed ultrasonic source, are given. An electronic apparatus, assembled for the most part from commercially available components to implement the measurement, is described. The output of the system is a strip chart recording of the strength of the ultrasonic field along a line. The advantages and limitations of the electronic system are discussed. A typical measurement made with the apparatus is shown and suggestions are given to extend the range of the apparatus.
Calculations of Random Fatigue of Hard-Spring Resonators
Authors: Smith P. W.
Published: September 2005

Computations have been made for the effect of a nonlinearity of the hard spring type upon the fatigue damage ensuing on excitation of a resonator by a stationary, broad-band, random Gaussian force. The fatigue theory used assumes simple accumulation of damage in proportion to a power of the peak values of response strain, without interactions between peaks. Two cases are distinguished: (a) strain proportional to displacement; (b) strain nonlinearly dependent on displacement, as is the surface fiber strain in a bar with pinned ends, responding in a single mode.

Numerical results are presented that indicate for case (a) a continuous decrease, with increasing nonlinearity, of the rate of accumulation of damage, while for case (b) this damage rate increases to a maximum as large as 3.4 times the linear estimate, and then falls below the value for linear response. Probability density (in response amplitude) of damage is greater at small amplitudes, and less at large, than for the linear case. The value of response amplitude of maximum damage density is also affected by nonlinearity.
Acoustic Properties of Anechoic Chamber
Authors: Olson N.
Published: September 2005

Measurements have been made on the performance of an anechoic chamber built for the National Research Council of Canada, adopting the inverse square law as the criterion of performance. Some deviations from the inverse square law were observed, and these were correlated with vibrational modes in the wedge bearing inner walls. It was shown that maximum amplitudes of vibration occur in certain regions of the walls and occupy frequency ranges which coincide with frequency ranges for maximum deviations from the inverse square law. The phase of the vibrations along the walls varies in the same manner as the phase of the incident sound wave in the room. Blocking all experimental points in one of the walls improved room response by a small but consistent amount. Treating regions of maximum vibration in the walls as extended sources and combining contributions from these with the sound field of the source in the room, it was possible to construct room characteristics similar to those observed.
Mechanism of the Middle Ear
Authors: Onchi Y.
Published: September 2005

A mechanical model of the middle ear is obtained from anatomical observations. The differential equations for the model are solved, and the solutions are found in good agreement with the impedance of the ear at the tympanic membrane measured in many earn of fresh cadavers. Thus, the mechanism of the middle ear is clarified theoretically as well as experimentally. The ossicular chain loaded with the impedance of the cochlea is found to be the most important factor controlling the impedance of the tympanic membrane. The ossicular chain has two resonances: the lower one due to the malleoincudal body, and the higher due to the stapes. Thus, the ossicular chain keeps the reactance of the tympanic membrane near or at its resonances. The function of the air cavities behind the tympanic membrane is found to be similar to but less than that of the ossicular chain. The apparent pressure gain by the middle ear for the cochlea is measured. From these data the frequency characteristic of the ossicular chain the impedance of the stapes are calculated. Moreover, it is found experimentally as well as theoretically that the transmission of the middle ear is not only increased by a lower impedance of the tympanic membrane but also by a higher impedance; transmission is increased by the tympanic membrane vibrating as a rigid cone attached to the ossicular chain even though such attachment increases the impedance of the tympanic membrane.
Speech Synthesis with Prerecorded Syllables and Words
Authors: Stowe Arthur N. , Hampton Donald B.
Published: September 2005

Lists of Psycho-Acoustic Laboratory sentences were used for synthesis of speech with prerecorded words and syllables as the building blocks. The sentences were phonemically transcribed with syllable boundaries indicated. The syllables were spoken in a random order with pauses between each syllable. The words were spoken in the same way without being phonemically transcribed. Two rates, slow and fast, were used for each type of building block, making four basic conditions. A different group of eight listeners heard each condition of synthesized speech. The mean scores, percent correct of the five key words in each sentence, for each condition were: fast rate syllables, 66.6%; fast rate words, 60%, slow rate syllables, 90%; slow rate words, 95.6%.
Laboratory Standard Ceramic Microphone
Authors: Newitt William
Published: September 2005

Microphones using barium titanate disk ceramics in conjunction with a split-tube diaphragm have been designed and constructed. Frequency response measurements were obtained by use of reciprocity techniques and by comparison with a known standard.

Sensitivities from −86 to −88 db referred to one volt per dyne per square centimeter, were obtained with a frequency response of plus or minus one db from 10 cycles to 30 kilocycles. The rugged construction and high stiffness of the microphone make it adaptable for use in high sound pressures, and for sound measurement in liquids.

The paper discusses theoretical relations pertinent to the development, describes the construction, and presents performance data of the microphone and associated electronic equipment.
On the Reflection of Sound from a Grating
Authors: Ingard Uno
Published: September 2005

The reflection of sound from a grating is discussed in the case when the slit width of the grating is small compared to half a wavelength of the incident sound. Then only the specular reflection will be present. The corresponding reflection coefficient is determined as a function of the angle of incidence of the sound and the results are applied to study the influence of a floor grating on the acoustic performance of an anechoic room.
Propagation of Nonaxially Symmetric Waves in Elastic Cylindrical Shells
Authors: Cooper R. M. , Naghdi P. M.
Published: September 2005

In a previous paper two general systems of equations of motion, designated as (I) and (II) for thin elastic cylindrical shells (which include the effects of both transverse shear deformation and rotatory inertia) were derived and employed in a study of the torsionless axisymmetric wave propagation in an infinite cylindrical shell. The character of the two systems of equations is such that, upon the neglect of transverse shear deformation and rotatory inertia, Eqs. (I) will reduce to those known as Love's first approximation, while Eqs. (II) will correspond to those given by Donnell.

This paper, again employing the systems of Eqs. (I) and (II), is concerned with the predictions of phase velocities and amplitude ratios, for nonaxially symmetric as well as purely torsional propagation of elastic waves in an infinite cylindrical shell. As in the previous case of axisymmetric propagation, comparison is made between the predictions of the two systems of equations and the conclusions are specified.
Density of Peaks in Random Response of Hard-Spring Resonators
Authors: Smith P. W.
Published: September 2005

The shape of curves for peak density of response of hard-spring resonators depends significantly on the choice of variable and the choice of normalization constant (the rms value of some variable). The curves for the variables: (1) displacement (bending strain in pinned bar) normalized to linear expectation of rms, (2) displacement normalized to actual rms, and (3) total strain (bending plus membrane, in pinned bar) normalized to linear expectation of rms—are compared with the linear case. Comments are made on the problems of comparing experimental data with these curves.
Acoustic Measurements Under Transient Temperature Conditions
Authors: Paine Ward L.
Published: September 2005

A quick and simple method of determining the effect of temperature change on the response of an underwater sound transducer is described. The method requires precooling or warming the transducer to the extreme temperature of interest and then monitoring its response while its temperature returns to ambient.
Rotational Waves in a Turbulent Liquid
Authors: Hartley R. V. L.
Published: September 2005

Equations are derived for the propagation in a liquid, in a state of fine scale turbulence, of a type of so-called transverse wave in which the elasticity is associated with the rotation of an element rather than with its shearing as in a solid. This elasticity is proportional to the density of the kinetic energy of turbulent motion. The equations are identical with those for Kelvin's gyrostatic ether model and, for small displacements, are the analog of those of Maxwell for free space.
On Wave Propagation in a Random Inhomogeneous Medium
Authors: Potter David S. , Murphy Stanley R.
Published: September 2005

This paper examines the calculation of the coefficient of variation of intensity for acoustic transmission in a randomly inhomogeneous medium. An equation for this coefficient is derived which is valid over the range of frequencies between the wave limit and the ray limit previously reported by other authors.
The Computation of Far-Field Radiation Patterns from Measurements Made near the Source
Authors: Horton C. W. , Innis G. S.
Published: September 2005

An analysis is made of two methods of predicting the far-field radiation pattern from pressure measurements made over a closed surface S, containing the source. One of these methods involves the use of Green's functions and yields two subcases according to the particular Green's function that is used. The Helmholtz formula, which results when one uses a Green's function of the form exp(ikR)/R, requires the knowledge of the normal gradient of the pressure ∂p/∂n over S in addition to the pressure p, but it leads to a formula that is relatively easy to evaluate. An approximation to ∂p/∂n is discussed. If, instead, one uses the Green's function which vanishes over the surface S, one can evaluate the pressure in the far field, in terms of measurements over S, of p only. The resulting formula is somewhat more complicated than the Helmholtz formula, but it does not require a knowledge of ∂p/∂n.

The second method is based on a proposal recently made by Pachner. It is shown, for the case of prolate spheroidal coordinates, that Pachner's method is completely equivalent to the second approach mentioned above. The applicability of these formulas is demonstrated with experimental data for a line hydrophone. Good agreement is obtained between the experimental radiation pattern and the theoretical patterns predicted by the formulas.
Noise-Induced Permanent Threshold Shift at 2000 cps and 4000 cps
Authors: Nixon J. C. , Glorig A.
Published: September 2005

Three samples of industrial workers were drawn from environments in which continuous, steady-state noise had average sound pressure levels in the octave bands from 150 to 4800 cps that ranged from 77 to 96 db. Each sample was sub-grouped according to length of time on job, yielding sub-samples whose mean times on job (mean exposure time for typical work years) ranged from less than one year to over 25 years. Median hearing levels were calculated for 2000 and 4000 cps for each sub-sample. Age effect (loss of auditory sensitivity due to aging) corrections were applied to the median hearing-level values appropriate to the mean ages of the sub-samples. The resulting values were defined as noise-induced permanent threshold shift (NIPTS). It is shown that: (1) there is a maximum NIPTS produced at 4000 cps which occurs within the initial 10 years of exposure to 8 hr/day exposures of continuous, steady-state noise of any intensity greater than 70–75 db in the 1200–2400 or 2400–4800 octave bands; (2) the maximum NIPTS values which are produced at 4000 cps are approximately equal to the noise-induced temporary threshold shift (NITTS) values predicted from the appropriate SPL's of each sample for 8 hr/day exposures; (3) there is no apparent maximum NIPTS occurring at 2000 cps within the exposure ranges studied; and (4) NIPTS for both 2000 and 4000 cps are monotonic functions of exposure time and SPL.
Response of the Skin to Focused Ultrasound
Authors: Bell Eugene , Argyris Thomas S.
Published: September 2005

Skin of mice has been irradiated with focused ultrasound of one megacycle frequency. Skin in the growing phase of the hair growth cycle becomes ulcerated within two days following treatment while skin in the resting phase of the cycle is relatively unaffected. It is concluded that the response of the skin to ultrasound depends upon the physiological state of the organ at the time of irradiation. Thermal changes which occur during irradiation with ultrasound were measured in resting and growing skin, and no significant difference in absorption of acoustic energy between the systems was found. Since the capacities of the respective systems for absorbing ultrasound are equal this factor can be eliminated as a possible cause for the differential response of the skin. It is also suggested that the differential response of the skin cannot be attributed to structural differences between resting and growing follicles. When skin is irradiated with focused light which produces the same thermal change as that produced by ultrasound, skin in growth is ulcerated and skin at rest is unaffected. The heating component of ultrasound appears to be the physical factor to which the biological response can be attributed.
Factors Influencing the Practice Effect for Auditory Thresholds
Authors: Loeb M. , Dickson C.
Published: September 2005

Investigators have reported appreciable practice effects for low frequency pure-tone absolute thresholds and no practice effects for thresholds at higher frequencies. It was suggested that practicing subjects are learning to discriminate between the signal and a low-frequency physiologic noise. No practice effect was observed at any frequency when thresholds were measured against a background of random noise. This finding would be predicted by the hypothesis advanced. However, efforts to induce a practice effect for a high frequency tone by introducing a faint, high-frequency narrow-band background noise were unsuccessful. Implications of the findings are discussed.
Studies on the Endolymphatic dc Potential of the Guinea Pig's Cochlea
Authors: Rice Edward A. , Shinabarger Edward W.
Published: September 2005

The effect of loud sound on the endolymphatic dc potential was studied in both normal and hypoxic animals. When the integrity of the cochlear wall was maintained, the endolymphatic dc potential decreased 5 mv with the onset of sound (1000 cps below 140 db) and recovered immediately when the sound was terminated. At intensities of 140 db and above, the dc potential irreversibly decreased. The effect of sound on the dc potential was the same for both normal and hypoxic animals. A negative dc potential was found in the scala media of hypoxic and dead animals. This potential survived the life span of the post-mortem microphonics. The positive dc potential returned on termination of hypoxia. Oxygen deprivation resulted in the dc potential decreasing before the microphonics. The possible significance of these findings to the physiology of hearing is discussed.
Condenser Microphones for Measurement of High Sound Pressures
Authors: Hilliard John K. , Fiala Walter T.
Published: September 2005

A series of small condenser microphones and accessory equipment has been developed for the measurement of high sound pressure levels. The paper derives expressions leading to the evaluation of the nonlinear distortion of the microphone, describes the construction of the several elements of the microphone system, and presents performance data. Four interchangeable microphones, all employing clamped glass plate diaphragms, provide linear measurements over a pressure range of 1 to 108 dynes/cm2. The microphones are 0.6 in. in diameter and their low directivity is shown by polar response patterns. A cathode follower tube is housed in a printed circuit base on top of which the microphone is mounted. Maximum output is 30 v rms. The equipment can be used over a wide range of temperature and barometric pressure and is sufficiently rugged to withstand severe overload and rough handling.
Ear-Insert Microphone
Authors: Black Raymond D.
Published: September 2005

It has been observed by several different technical groups that an acoustic transducer placed at the ear can be used as a microphone to pick up the voice of the wearer. This paper presents the results of an investigation to determine the various factors which make possible the use of a microphone in the ear.

The investigation, using a laboratory model dynamic ear-insert microphone and a protective headset, determined the relative importance of the two principal paths that conduct sound pressure from the mouth to the outer ear canal: (1) The air path around the head, and (2) the path through the head. The voice spectrum in the outer ear canal, contributed by the path through the head, was also obtained.

It appears that the ear-insert microphone could compete with a conventional microphone in front of the lips only in an application where it is difficult to use the conventional microphone because of its size or its interference with other equipment. The investigation forms a basis for further study to determine whether the ear insert microphone has a future as a practical communications device.
Improved Nickel-Base Alloys for Magnetostrictive Transducers
Authors: Clark C. A.
Published: September 2005

Dynamic magnetostrictive properties have been measured for nickel-base alloys containing up to 10% cobalt, with from 0 to 6% chromium. The maximum value of electromechanical coupling coefficient 0.51 occurs in a binary alloy containing 4.5% cobalt, balance nickel, for which the magnetocrystalline-anisotropy constant is zero. The maximum value of potential electroacoustic efficiency for resonance frequencies below 100 kc/sec is found, however, in a ternary alloy containing 1.4% cobalt, 2.3% chromium, balance nickel.

It is concluded that the binary alloy is the most suitable material for the magnetostrictive element of receivers, such as hydrophones, particularly where a reasonably flat response is sought. The ternary alloy, because of its lower eddy-current losses, is to be preferred for generating high-frequency acoustic power.
Generation of Intense Audio Sound Fields Utilizing Arrays of Multiple-Driver Horns
Authors: Levy Sidney E. , Carlisle Richard W.
Published: September 2005

There are several major applications for intense audio sound fields: the outdoor propagation of speech and of warning signals, and the sonic fatigue testing of missile and aircraft components. In these applications, several factors combine to make it necessary to limit the portion of the frequency spectrum covered by any one loudspeaker unit. In order to provide adequate power capacity, selection is required between the alternatives of (a) using a large number of identical drivers, (b) using a plurality of drivers each especially designed for a selected portion of the frequency range, and (c) using combinations of these arrangements.

In an array currently being used for sonic-fatigue testing, a plurality of large open cone loudspeakers is used for low frequencies, and a plurality of horns is used for middle and high frequencies. Each horn is driven by several drivers.

The driver voice coil and diaphragm proportions have been optimized to withstand fatigue stresses under the thermal conditions encountered. The driver is rated at 50-w input for program material.

Horn assemblies are available having throat arrays for mounting 6, 12, or 24 drivers. Various applications will be illustrated.
Threshold for Thermal Noise as a Function of Duration and Interruption Rate
Authors: Thurlow W. R. , Bowman R.
Published: September 2005

Experiments are reported on temporal summation at threshold for thermal noise. Durations from 1 to 850 msec and repetition rates from 1 to 100 per sec were used. Results show that threshold decreases as a function of duration for all repetition rates. Thresholds also decrease as a function of repetition rate, though the effect of repetition rate is not so marked as that of duration, and becomes even less so at long durations.
Information in Simple Multidimensional Speech Messages
Authors: Webster John C.
Published: September 2005

Simultaneous pairs of four-bit messages were presented to listeners at rates of two pairs every 4 sec (4 bits/sec), three pairs every 4 sec (6 bits/sec), four pairs every 4 sec (8 bits/sec), and six pairs every 4 sec (12 bits/sec). Each message of the pair was either [a] or [i], said by a male or a female, as a question (rising inflection) or a statement (falling inflection), and heard in either the right or the left ear.

Sequences were made that were balanced (1) between ears, (2) between male and female voices, (3) between [a]'s and [i]'s and (4) between questions and statements. The subject sometimes listened to both messages but usually listened only for the messages (1) in one ear, (2) of one voice, (3) of one vowel sound, or (4) of one inflection.

The best subject could receive correctly about 6 bits/sec whether this was one of two messages at the 12 bits/sec rate or both of two at the 6 bits/sec rate.