bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Pressure Low-Frequency Microphone Calibration
Authors: Starr Edward A.
Published: September 2005

Calibration of microphones at high sound-pressure levels and low frequencies is of interest in the measurement of sound propagated over large distances from large rocket boosters or from sonic booms, and for some psychoacoustic experiments. A pistonphone has been developed for microphone calibration that generates sound-pressure levels from 110 to 140 dB re 2×10−4 μbar in 10-dB increments over the frequency range of 1–200 cps, and from 140 to 170 dB re 2×10−4 μbar over the range from 5 to 140 cps. The accuracy of the measurement is within ±0.2 dB over most of these ranges. Corrections required for thermal losses to the walls at low frequencies and for wavelength effects at high frequencies are discussed. The lower-frequency limit can bc extended at the expense of the higher-frequency limit.
Pressure Vessel for Farfield Sonar Transducer Calibration
Authors: Green Charles E.
Published: September 2005

The calibration of sonar transducers under pressure has been a difficult and lengthy task. A pressure vessel has been designed and constructed specifically for such calibration, with walls as acoustically transparent as possible and yet physically strong enough to withstand reasonable internal pressures. The transducer to be calibrated is placed within the vessel and the whole assembly mounted for calibration. The second transducer used in the measurement is located outside the vessel and at the regular calibration distance. The acoustical path from one unit to the other is through the walls of the vessel. A surface-mounted water pump controls the internal pressure. This system subjects the test transducer to high static water pressure while the calibration is actually carried out in shallow water. The present vessel will accept transducers as large as 20 in. across and 36 in. long and will hold pressures up to 800 psi. The vessel has been successfully used over the range from 1000 cps to 250 kcps without interference from mechanical resonances, pattern distortion, or high attenuation.
Electrostatic Microphones with Foil Electret
Authors: Sessler G. M. , West J. E.
Published: September 2005

While the performance of electrostatic microphones with foil electrets is similar in many respects to that of conventional condenser microphones, they have considerably higher capacitance and do not require a dc bias. Recent studies on electret microphones have been extended to a number of dielectric materials. Measurements of the change in sensitivity as a function of time indicate that microphones with fluorocarbon electrets are superior to systems with polyester electrets at room temperature and at elevated temperatures. The results also indicate that the change in sensitivity of electret microphones depends on the stability of the surface charge of foil electrets and on mechanical parameters of the system.
Measuring Noise Cancellation of Carbon Transmitters while Compensating for Self-Generated Noises
Authors: Schiller Elaine
Published: September 2005

The “signal-to-noise” test box for differential microphones described by the Cruft Laboratory in 1945, which uses an aircraft-noise spectrum at 115 dB SPL, is the only standardized method for evaluating carbon noise-cancelling transmitters. For carbon transmitters used in a variety of noise fields, the Cruft box is inadequate. Described in this paper is a noise spectrum that can be used to measure the actual noise cancellation of the carbon transmitters and a method for predicting how the carbon noise-cancelling transmitter will perform in any other known spectrum. A peculiar self-generation of low-frequency noise has been investigated at length for this paper and must be taken into account when computing the articulation index for a carbon transmitter. Details of this phenomenon are presented, along with predicted and measured noise response curves in various noise fields. An evaluation of the Cruft noise box is also presented.
Operationally Defined Homonyms of One Syllable in the English Language
Authors: Bhimani B. V. , Earl L. , Mitchell R.
Published: September 2005

When the phonetic representations of one-syllable words in the Shorter-Oxford Dictionary were compared, some phonetic forms had more than one graphic representation. The graphic representations corresponding to a single phonetic form were operationally defined as a set of homonyms of the phonetic form. The sum of graphic words in such sets is about 1700. When plural and past forms of each word were compared with the citation forms of other Words, about 700 additional homonyms emerged, showing that, in a total population of about 5700 one-syllable words, about 2500 are ambiguous in their phonetic representation. Since the Shorter-Oxford Dictionary has relatively fine phonetic distinctions, repeating the experiments on the American College Dictionary, the Jones English Phonetic Reader, Webster's Third International Dictionary, and Pronouncing Dictionary by Kenyon and Knott yielded additional homonym forms. Thus, in distinguishing among the words of English, the orthographic form proves to be more useful than the phonetic representations. In this paper, illustrations of the homonyms, the near homonyms, and the questionable homonyms are given and discussed. [Work supported by Lockheed Independent Research.]
Experiments in Pitch Detection
Authors: Wood David E.
Published: September 2005

This paper describes the results of experiments in the automatic detection of the quasiperiodic “pitch” frequency of the voiced portions of speech. The approach tested transforms the energy pulsations of voiced speech to frequency components that are accurately detected and measured by a novel type of spectrum analysis. Experiments have shown that correct pitch is consistently extracted from the general utterances of both male and female speakers. Initial pitch transitions and other variations are faithfully reproduced. Pitch can also be extracted from speech in which the fundamental frequency has been eliminated, as can occur in Vocoder communication systems. The technique can be implemented in a practical pitch-extraction device. Spectrograms and other demonstrations are included to show the relations of measured pitch to original speech characteristics.
Orthogonal Polynomial Representation of Vowels
Authors: Young James R.
Published: September 2005

Laguerre and Hermite orthogonal polynomials have been used to approximate single pitch-period segments of 6 vowels produced by each of 2 talkers, one male and one female. Using mean-squared error as a quality criterion, approximation error as a function of polynomial complexity is studied across vowels and talkers. The effect of varying pitch is treated in the manner of time scaling and presented separately. Both polynomial representations permit adjustments of the weighting function used in the computation of coefficients, and the effect of these adjustments is discussed in terms of changes in approximation error. The computer algorithms used for generating the approximating polynomials are presented and possible real-time polynomial analyzers are discussed. [This work was supported by Stanford Research Institute.]
Analysis and Presentation of Confusion-Matrix Data
Authors: Hill David R.
Published: September 2005

As part of the work on an automatic speech recognizer, an approach has been developed to the analysis and presentation of results from confusion tests on potential vocabularies. The method depends on taking the null hypothesis that, if errors occur in a series of responses to a stimulus word. the errors are distributed amongst the response as alternatives in a random manner. This would give rise to a Poisson distribution for the error responses to a particular stimulus word. The fit of the observed distribution to the theoretical distribution may be investigated and the levels of significance determined for the observed deviations. The final confusion matrix may then be drawn up to show only those confusions which are significant at, and above, the level of significance that the experimenter deems critical. A second, slightly lower, level may also be shown to indicate the spread occurring when the criteria for significance are relaxed somewhat. The final matrix preserves all the essential information from the experiment shorn of the redundancy embodied in the figures.
Speaker Recognition by Humans
Authors: Clarke Frank R.
Published: September 2005

These experiments are predicated on the assumption that no set of vocal attributes can be said to be characteristics used by humans for distinguishing among talkers unless recognition can be achieved solely on the basis of the listeners' ratings of these characteristics. Five graduate students in speech sciences were given a multiple-choice speaker-recognition test involving 20 talkers. With a new sample of talkers, these listeners attempted to define parameters of the speech signals useful in distinguishing among talkers. Six scales showing the highest reliability and validity were chosen, and the listeners rated several samples of each of the original 20 talkers on these scales. At the completion of the experiment, these samples were then rearranged by the experimenter in the form of a multiple-choice test and Euclidean distances between rating vectors were used in an attempt to identify the correct speaker for each item. Performance based on these ratings was approximately that obtained by the listeners when they took the test “live.” Some implications of these experiments are discussed. [Work supported by Decision Sciences Laboratory, ESD, U. S. Air Force Systems Command, Bedford, Massachusetts.]
Decision Procedures for Discriminating between Speakers
Authors: Becker Richard W.
Published: September 2005

Decision procedures are considered in which one of a number of alternative points must be identified as belonging to the same set as a given stimulus point. If the points are all described by values on n characteristics, the decision may be made by calculating the distance from each of the alternatives to the stimulus in the n-dimensional feature space. If the features are not independent or not equally useful, the decision procedure may be improved by applying a linear transformation to the space before calculating distances. Since the decisions are based upon single-point representatives of sets rather than sets of points, standard methods of obtaining optimal transformations are not useful. Possible criteria of optimality, useful classes of transformations, and methods of obtaining good transformations are discussed. Transformations are applied to data in which expert listeners rated sentences from different speakers on 6 voice characteristics. The inability of diagonal transformations to improve this decision procedure is related to the nature of the speaker discrimination task. [Work supported by Decision Sciences Laboratory, ESD, U. S. Air Force Systems Command, Bedford, Massachusetts.]
Effects of Frequency Filtering upon the Information Content and Structure of Voice Ratings
Authors: Voiers D. , Miller J. F.
Published: September 2005

Using a multidimensional voice rating form, each of 7 listening crews rated the voices of 16 male speakers under a different frequency-pass condition. Results are presented in terms of total amount of speaker-identity information transmitted under each condition. Also described are the effects of each condition upon the information transmitted via selected perceptual dimensions or perceived acoustic traits. [The research reported in this paper was sponsored in part by the U. S. Air Force Cambridge Research Laboratories, Office of Aerospace Research.]
Numerical Calculation of the Acoustic Field Owing to a Point Source on a Rigid Sphere
Authors: Lightner G. Samuel
Published: September 2005

To make this calculation, an array of 151 points was chosen on the sphere. The normal flow through the area associated with each of these points owing to a unit real source at each of the other points was calculated. In the remainder of the calculation, fictitious point sources were placed at the selected points such that they would cancel any volume flow through the associated areas because of the remaining sources. A Gauss-Sidel iteration was used to solve these equations for the source strengths. The field at a point off the sphere is then the superposition of the fields owing to the original source plus the fictitious sources. Results are shown for several wavelength-to-radius ratios. This solution may be compared with that in Vol. 2, Sec. 328 of Lord Rayleigh's Theory of Sound. [This work is a portion of a senior project in physics in partial fulfillment of the requirements for the degree of Bachelor of Science in Randolph-Macon College. The help of Dr. Sanford P. Thompson, project adviser, is greatly appreciated.]
Fields Radiated from an Acoustic Line Source above a Fluid-Fluid Interface
Authors: Cretella J. P. , Spence J. E. , Buratti R. J.
Published: September 2005

The problem of determining the fields radiated from an acoustic line source above a fluid-fluid interface leads to the evaluation of a contour integral that involves two pairs of branch points in the complex-wavenumber plane. By using the steepest-descent method, asymptotic expansions that are valid only in the far field have been obtained by various investigators. These expansions, however, furnish little information on the transition region from the near to the far field. In this paper, we employ a series of transformations in the complex plane in conjunction with a generalization of the method of steepest descent to obtain representations that are valid from the source region to the far field. The results are expressed in terms of Hankel and algebraic functions, both of which are easily computed. As a result, we are able to prepare plots that delineate the character of the acoustic fields.
Two-Dimensional Acoustic Fields and Amplitude-Phase Space
Authors: Simmons J. W. , Harbold Mary L.
Published: September 2005

A mapping of two-dimensional real space, in which a time harmonic acoustic field exists, into a polar amplitude-phase space is considered. This mapping defines a set of “folding lines” that partition real space into connected regions over which the mapping is one to one. The “folding lines” are shown to be those curves along which the circulation of the vector intensity is zero. A computer has been used to determine these lines for plane-wave scattering from hard and soft cylinders for ka values of 0.5–6.0. The results yield an insight into the nature of the diffracted wave not obtainable from amplitude and phase calculations alone. [Work supported in part by a National Science Foundation grant.]
Use of Toroidal Wavefunctions for the Free-Flooding Ring Transducer
Authors: Sherman Charles H. , Parke N. G.
Published: September 2005

The problem of acoustic radiation from a thin torus has been solved by use of the toroidal wavefunctions derived by V. H. Weston. When a suitable normal velocity on the surface of the torus is chosen, this problem provides an adequate model for calculating the far field of free-flooding ring transducers. Although such transducers are commonly used as underwater sound sources, their development has long suffered from the lack of such a theoretical model. Calculations of the radiation pattern, directivity index, and radiation resistance are in good agreement with published measurements for single transducers and coaxial arrays. However, the nearfield quantities given by this model, such as radiation mass loading, are not adequate for ring transducers and will require more realistic models. Such models can also be based on the toroidal wavefunctions, but will involve more numerical work than the thin torus model. [Work supported by U. S. Navy Underwater Sound Laboratory.]
Problem in Dynamic Thermoelasticity
Authors: Tsui Y. T.
Published: September 2005

This paper deals with the dynamic treatment of a transient thermoelastic problem for an elastic half-space that is exposed to step temperature and velocity on its entire plane boundary and is constrained against transverse displacements. The stress distribution pertaining to this problem, whose plane boundary is subjected to step- and/or ramp-type temperature only, was previously treated by Danilovskaya [Prikl. Mat. i Mekhan. 14, 316 (1950)], Mura [Proc. Japan Natl. Congr. Appl. Mech., 2nd, 9 (1952)], and Sternberg et al. [J. Appl. Mech. 26, 503 (1959)]. In physical reality, when the boundary experiences temperature variations, it often also experiences velocity variations. A comparison of present results with previous results reveals that the stress distributions are changed considerably once the velocity variation on the boundary is considered.
Ultrahigh-Frequency Pulse Measurements in Relaxing Liquids
Authors: Hunter Joseph L. , Dardy Henry D.
Published: September 2005

Ultrasonic-absorption measurements have been carried out to 550μ Mc/sec in several relaxing as well as nonrelaxing liquids, including carbon disulfide and halogenated methanes. Problems of measurement where the absorption is extremely high (of the order of 25 000 dB/in. are discussed and absorption data are presented. Marked contrasts are found between the behaviors of different relaxing liquids over wide frequency and temperature ranges. The data are interpreted in terms of the vibrational specific heats of the liquids, with particular attention given to the problem of deciding between single and multiple relaxation times. The apparatus was a two-crystal absorption cell with special refinements to preserve parallelism. [This work was supported by the Acoustics Branch of the U. S. Office of Naval Research.]
Thermal-Relaxation Absorption in Carbon Dioxide/Water-Vapor Mixtures
Authors: Lewis James W. L. , Lee K. P. , Shields F. Douglas
Published: September 2005

Sound-absorption and -dispersion measurements have been made using the tube method on CO2-H2O mixtures over the temperature range of 23°–195°C. A single relaxation time was found to describe adequately both the absorption and dispersion curves. The reciprocal of the relaxation time at each temperature was found to be linearly dependent on the concentration of H2O. The relaxation time τAB was calculated at each temperature, and τAB was found to increase as the temperature increased. A significant result is that log τAB exhibited no minimum value when plotted versus T−13, as has been previously reported by Eucken and Numann, but rather log τAB shows a linear decrease versus T−13. The number of collisions Z10(AB) necessary to deexcite the lowest vibrational mode of CO2 has been calculated from the measured relaxation time and is essentially temperature-independent. [This work was supported by the U. S. Office of Naval Research.]
Vibration Isolator for Stable Platforms
Authors: Marshall Philip
Published: September 2005

Inertial navigation systems require precise angular alignment with the flight vehicle, particularly when vibration isolators are utilized. This paper describes an isolator arrangement that provides a soft suspension along all axes in translation (18 cps) and a rigid suspension about all axes in rotation (above 30 cps). Angular returnability is better than 30 sec of arc. Both friction and viscous dampers can be utilized to limit the resonance amplification to values of 5 or less. A description of how mechanical-impedance tests are used to evaluate the performance of viscous dampers as a function of frequency, is also described. Vibration transmissibility curves are given for a typical isolation system.
Measurement of Natural Frequencies and Fluid Loading of Propellers, Using Mechanical-Impedance Techniques
Authors: Schloss Fred
Published: September 2005

The resonant frequency and the mass load of vibrating full-scale propellers are calculated from experimental data of scaled-down models. The method is described, and data for a variety of different propellers are presented in tabulated form.
Series Representation of Structural Mobility
Authors: Neubert V. H.
Published: September 2005

In investigating the behavior of subcomponents of a structural system, attention is often given to the meeting of mobility or impedance at mounting or junction points. Thus, if the mobility at a point in a certain frequency range is given, a black box might be devised that contains a structural model designed to duplicate the desired mobility. Various methods are discussed for arriving at models based on different forms of series solutions for mobility of linear systems. Models are presented for a particular example: a uniform, thin bar with free ends. Although it is well known that a model with a large number of discrete elements will adequately represent a uniform bar, the possibility is demonstrated of furnishing a model containing only a few elements, for a certain frequency range. The mobility of combinations of models is also presented. Through the Fourier-transform relationship between mobility and transient response, it is shown that the models accurate for predicting steady-state response are accurate for transient response. [This research was carried out as part of a program supported by the U. S. Office of Naval Research.]
Stroboscopic Laminagraphy as a Method in Laryngeal Research: Preliminary Data
Authors: Hollien Harry
Published: September 2005

Stroboscopic laminagraphy was developed in order to obtain coronal cross-sectional x-rays of the human vocal folds that are not contaminated by the limitations of standard laminagraphy. These limitations occurred because standard laminagraphy provides only a single exposure (overtime) of the rapidly moving vocal folds. Hence, the outlines of the folds resulted from a blur of many complete vibratory cycles and did not represent them in any particular position during the cycle. Thus, their shape and size could have been contaminated by movement artifacts and the associated measurements questioned. The research technique of stroboscopic laminagraphy (STROL) is described by means of a 6-mm sound motion picture film. Included in this film are illustrations of how STROL. may be used to study the dynamic movements of the folds in coronal cross section. Finally, a separate description is presented of the measure-thickness of the vocal folds. This discussion includes prement technique that provides information on the area and liminary data on the relationship of vocal-fold thickness to fundamental frequency of phonation. [Work supported by the National Institutes of Health, U. S. Department of Health, Education, and Welfare.]
Microtemporal Synchronization System for Ultra-high-Speed Photography
Authors: Dew Donald , Moore Paul
Published: September 2005

There is a need to synchronize images of the vocal folds photographed by ultra-high-speed photography with representations of the acoustic signals generated by the larynx. This paper is a report of a system that provides such synchronization and of its application to investigations of voice production. This technique involves the simultaneous identification, during high-speed photography, of a single instant of time on (a) an oscillographic trace of the acoustic wave from the larynx, (b) a single image of the vocal folds, (c) an oscillographic trace of a 5000-cps timing signal, and (d) a magnetic recording of the vocal sound. [Work supported by the National Institutes of Health, U. S. Department of Health, Education, and Welfare.]
Review of Formant Vocoder Technology
Authors: Campanella S. J. , Coulter D. C.
Published: September 2005

The formant vocoder has now been under investigation for use as a speech-compression system for more than a decade. During that time, significant advances have been made in the technology of the analysis and synthesis portions of the formant vocoder, and in the encoding of the parametric control signals for communication of the speech information at data rates normally of 1200 bit/sec and as low as 600 bit/sec. The consequence has been considerably improved vocal quality and articulation. Also, a voice-excited operation mode has been developed for the formant vocoder that is designed to provide high-quality speech transmission at a data rate of 4800 bit/sec. In this paper, some of the more important aspects of the formant-vocoder system design are to be discussed. These include adaptive techniques for formant-frequency tracking the use of the serial vocal analog for synthesis, encoding techniques for transmission of the vocoder parameters in binary form, and the voice-excited mode of operation of the formant vocoder.
Injury Induced in Isolated Muscle Fiber by Locally Applied Ultrasound
Authors: Wilson Walter L. , Wiercinski Floyd J. , Schnitzler Ronald M.
Published: September 2005

A muscle fiber was sonated by means of a needle machined into the tip of a steel acoustic horn. During sonation of a fiber in Ringer solution, there is a breakdown of cross striations in the region close to the needle tip and a movement of sarcoplasm toward this injured region. At cessation of sonation, the movement of sarcoplasm towards the injured region ceases and reverses direction: striation breakdown proceeds along the length of the fiber. Sonation does not evoke injury or sarcoplasmic movement when a fiber is immersed in paraffin oil, calcium-free Ringer, or in isotonic solutions of KCl, NaCl, or Na oxalate. If any one of these solutions is replaced by unbuffered Ringer, or if calcium ion is added to any one of these solutions, movement and injury can be evoked. Sarcoplasmic movement and injury occur in CaCl2 solutions as dilute as 0.001 M. This response to ultrasound appears to be calcium-ion-dependent. Apparently sonation increases membrane permeability to calcium ion. [Work supported by the National Institutes of Health, U. S. Department of Health, Education, and Welfare.]
Pressure Disturbances of Impulsive Line Heat Sources
Authors: Remillard W. J.
Published: September 2005

The pressure disturbance produced by an impulsive line heat source is described. Physically, the line source may represent a lightning stroke and the pressure disturbance may represent the resulting thunder. The analysis begins with the Navier-Stokes equations, which describe flow in a compressible, heat-conducting, viscous medium. These equations are linearized and the flow is represented as the stun of a transverse and a longitudinal component. Laplace transforms are used to reduce the linear partial differential equations that describe the longitudinal flow to ordinary ones. These equations are solved for the Laplace transform of the velocity potential. The inverse transform is then obtained by approximation methods. Finally, the functional relation between the velocity potential and the pressure disturbance is derived and used to determine a description of the resulting sound wave. [This research was supported in part by the Weather Radar Branch, Meteorology Laboratory, U. S. Air Force Cambridge Research Laboratories, Office of Aerospace Research.]
Effect of Hydrostatic Pressures on Magnetostrictive Vibrators
Authors: Feith K. E. , Whymark R. R.
Published: September 2005

The investigation detailed here was carried out on a ring magnetostrictor vibrating in radial mode and exposed to hydrostatic pressures ranging from ambient to 5000 psi. The hydrostatic environment was produced in an oil-filled annular pressure cavity dimensioned so that the radiating surfaces of the ring were separated by less than 110 of a sound wavelength from the cavity walls. Pressure-induced changes in the oil radiation impedance were thereby minimized and amounted to less than 5%. Analysis of electrical-impedance diagrams obtained at polarization levels up to 25.2 Oe showed that the magnetic permeability μr, changed by less than 1% between ambient pressure and 5000 psi while the magnetostriction constant λr changed by 4% over the same pressure range. The transducer mechanical “Q” was constant to within 5% over the 5000 psi pressure range even though the laminations were “soit” bonded. Quasistatic measurements of λr, and μr confirmed the previous findings to within the experimental-error limits (5%). These results are compared with measurements previously reported for axial, compressive, bonding of a bar magnetostrictor. [Work was supported by the U. S. Office of Naval Research.]
Ocean as a Filter
Authors: Parvulescu Antares
Published: September 2005

If an arbitrary signal is transmitted from a fixed point in the ocean to a fixed receiver, the received signal will be a highly modified, or distorted, version of the transmitted signal. The modification of the “input” into the “output” can be considered analogous to that performed by an electrical network, or filter. It is shown that this is not merely an analogy but a legitimate generalization, i.e., that the electric filter is merely a simple instance of the same general process. This generalization is used to discuss the following problems: (a) analysis of the ocean filter; (b) synthesis of a prescribed filter; (c) measurement of a filter by impulse response and by frequency-response methods; (d) correlation between two similar filters [see A. Parvulescu, “M.E.S.S. Processing,” J. Acoust. Soc. Am. 33, 1674(A) (1961)]; (e) inversion of a given filter. [Hudson Laboratories, Columbia University Informal Doc. No. 73. Work supported by the U. S. Office of Naval Research.]
Stability of Propagated Sound. II
Authors: Parvulescu Antares , Mitchell Dana D.
Published: September 2005

We have examined in two experiments the spatial fine structure of propagation between slightly displaced transducers, as well as the temporal stability in a fixed geometry. In February 1963, we used the USNUSL facility on Fishers Island to study propagation over shallow water in Block Island Sound. With fixed geometry, relative phases between arrivals showed no variation over 12 h. For transducer displacements increasing in steps of 2.5 ft, the crosscorrelation coefficient showed two kinds of decay: over some bottoms, the decay was exponential with a constant of about 50 ft; elsewhere it was exponential cosine (like a damped oscillation), with nulls at about 75 and 150 ft. In September 1963 in the Straits of Florida, and with the collaboration of John C. Steinberg of the University of Miami, we found that at 15 nm a displacement of 2 ft was sufficient to grossly change the relative phases of the diverse arrivals at the fixed shallow hydrophone. In a fixed geometry at 4 nm over shallow water, temporal stability was so good that we were able to use a frequency-response measurement in lieu of an impulse-response measurement. [Hudson Laboratories, Columbia University Informal Doc. No. 75. Work supported by the U. S. Office of Naval Research.]
Instrumentation and Techniques for Measurement of Sonic-Boom Signatures
Authors: Hilton David A. , Newman James W.
Published: September 2005

Special considerations are involved in the selection of instrumentation for meaningful sonic-boom measurements. Because of the nature of the sonic-boom pressure signature, the requirements include usable frequency response from nearly dc to several thousand cycles in the pressure range 0.1–10 lb/ft2. A specially developed NASA instrument system is described, along with techniques of measurement. The problems of vibration isolation, wind screening, long cable lengths, and field calibrations are defined, and some sample data are presented.
Sic Transit Sonitus
Authors: Hunt F. V.
Published: September 2005

Appropriate signal processing can make available a “count” or “lockup” signal when a moving source passes near a monitoring receiver. The rectified and filtered output of the sensor is sampled periodically and a “one” or a “zero” is delivered to a shift register according to whether the current sample is larger or smaller than the one before. For noise alone, ones and zeros accumulate in random sequence, but during a source transit the level at first increases monotonically and then decreases. After a transit, therefore, the (2N+B)-stage shift register will contain N ones in unbroken sequence, B indecisive digits that are ignored, and N zeros in another unbroken sequence. This unique 2N-digit binary number can be recognized with a simple AND circuit, and the probability of it occurring by chance is only 2−2N. A computer-aided study indicates that a detection probability of 90%, with a false-alarm rate of 10−6, can be achieved for quiet slow sources whose signal-to-noise ratio at the point of closest approach is about −6 dB, and the detection range is almost never less for faster and noisier sources. [Work supported in part by the U. S. Office of Naval Research.]
Amplitude Learning in the Sequential-Clipper Crosscorrelator Detection Receiver
Authors: Kimball Christopher V.
Published: September 2005

A comparison is made between an adaptive sequential-clipper crosscorrelator and the adaptive nonclipping sequential receiver for the case of a signal known except for amplitude; i.e., amplitude is specified by a probability distribution. Both receivers update distributions on the signal amplitude during the observation process to learn the transmitted signal amplitude and, consequently, improve receiver performance. This study compares the amplitude learning of the two receivers during one step of the sequential procedure. Assuming the same initial information, a fixed small-amplitude signal is applied to the input of each of the receivers and the distributions after observation are studied. From these distributions, the amplitude learning of the sequential-clipper crosscorrelator receiver is compared with that of the amplitude-utilizing receiver to provide a measure of the efficiency of the clipper crosscorrelator receiver in learning the signal amplitude. The measure obtained is analogous to the well-known detection efficiency of 2/π. [Work supported by the U. S. Office of Naval Research Acoustics Programs (Code 468).]
New Calculation Methods for Echo-Ranging Ambiguity
Authors: Weston D. E.
Published: September 2005

Signal ambiguity in correlation echo-ranging may often be calculated by a correlation process on the envelopes of pulse intensity in a frequency-time diagram. The ambiguity for crossing noise ribbons depends only on the ribbon lengths and the angle of crossing. The mean ambiguity has the same value for crossing lines, and this is the key result of the paper. The ambiguity pattern for touching curved lines is similar to that for touching curved noise ribbons of a definite width. As an example the entire ambiguity diagrams for straight or slightly curved lines may be simply calculated, in both the narrow- and wide-bandwidth cases. Simple formulas are given for the Doppler tolerance and the behavior near Doppler invariance. [Hudson Laboratories of Columbia University Informal Documentation No. 78. Work supported by the U. S. Office of Naval Research.]
Wall Vibrations in Organ Pipes and Their Effect on Tone
Authors: Backus John
Published: September 2005

The wall vibrations of seven different flue organ pipes were measured while the pipes were sounded normally, using an accelerometer of very small mass constructed from a phonograph pickup. It was found that the wall-vibration pattern obtained for a given harmonic of the pipe tone could be matched quite precisely by mechanically driving the pipe at the harmonic frequency with a vibrated rod in contact with the lip of the pipe. Sound levels at a selected point were measured both for the pipe sounding normally and for the pipe artificially vibrated with the same acceleration level. Results for the pipes tested showed that the sound levels produced by the wall vibrations are a negligible part of the pipe tone. The effect of the wall vibrations on the internal standing wave was also investigated. A larger tube was placed around the organ pipe, sealed to it at one end, and the intervening space filled with water. The amplitude and frequency of a given harmonic produced by blowing the pipe were then observed as the water was drained off. In no case could any change be detected. The acceleration levels obtained were compared to those obtained on a number of pipes of a small church organ and found to be comparable. It is concluded that the wall vibrations of an organ pipe do not contribute to its tone either by radiating sound or by affecting the internal standing wave.
Computer Study of Trumpet Tones
Authors: Risset J. C.
Published: September 2005

A study of the trumpet tone quality has been undertaken to determine the important physical correlates of trumpet timbre. Musical fragments played by a professional trumpet player have been recorded; selected tones have been converted into digital form by sampling at 10-kcps rate for subsequent spectral analysis. The computer analysis has yielded displays of the amplitude of each harmonic as a function of time (one point per fundamental pitch period). From these displays and computer sound-generation programs, tones were synthetized that proved to be indistinguishable from the real tones by skilled musicians. By systematically altering the tones' parameters, it was found that a few physical features were of utmost aural importance: the attack time (which is shorter for the low-frequency harmonics than for the high-frequency ones), the fluctuation of the pitch frequency (which is of small amplitude, fast, and quasirandom), the harmonic content (which becomes richer in high-frequency harmonic when the loudness increases). From only these features, it was possible to synthetize brasslike sounds.
Theory of Flue-Pipe Sound Generation
Authors: Elder S. A.
Published: September 2005

External radiated sound in the near field of the mouth of flue organ pipes or recorders is in phase with the internal field and may be calculated from the standing-wave-pressure amplitude within the pipe (Nyborg's law). Pipes voiced for small-mouth radiation impedance are driven at (approximately) a velocity antinode. Here the jet-edge system possesses asymmetry under dynamic conditions. The external sound-pressure amplitude, being proportional to the standing-wave flux in the mouth, depends only on jet speed and cross section, independent of pipe Q, since the standing-wave flux is comparable to jet flux. When voiced for larger-mouth impedance, the driving point approaches a velocity node condition. As this happens, the jet-edge system becomes symmetrical. Most efficient driving occurs when the peak sound pressure near orifice approaches jet stagnation pressure, since this case represents best “matching” to driver. With recorders, best match occurs for notes near the middle of the scale, causing the instrument to be loudest in this range. [Work supported by the U. S. Office of Naval Research.]
Effects of Sonic Boom on People: St. Louis, Missouri 1961–1962
Authors: Nixon Charles W.
Published: September 2005

The vicinity of St. Louis, Missouri, was repeatedly exposed to sonic booms ranging in overpressures up to about 3 lb/ft2 during 1961–1962. Data obtained from over 2300 direct interviews, analyses of complaints, and engineering evaluations of alleged damage are related to information on aircraft operations and sonic-boom overpressure measurements. Most residents interviewed indicated some interference with routine living activities, yet less than 1% filed formal complaints. Alleged building damage was superficial in nature, and consisted mostly of cracks in brittle surfaces. There were no reports of direct adverse physiological effects.
Assessment of the Sonic-Boom Problem for Future Air-Transport Vehicles
Authors: Baals Donald D. , Foss Willard F.
Published: September 2005

The economic feasibility of the supersonic transport is critically dependent upon specification of the sonic-boom requirements. Aircraft design techniques and modifications to the mission profile are evaluated relative to the sonic-boom intensity. An intermediate-range, domestic, supersonic transport optimized from considerations of the sonic boom is analyzed relative to potential boom levels. Future air-transport vehicles, such as the hypersonic transport, recoverable space booster, and ballistic transport, are discussed relative to their sonic-boom characteristics.
Sound Attenuation in Helium-Argon Mixtures
Authors: Law A. , Koronaios Nicholas , Lindsay R. Bruce , Stavseth R. M.
Published: September 2005

Sound-attenuation measurements have been made in binary gas mixtures of He-Ar (He mole fraction from 0 to 0.80) at 70 kc/sec in the ω/p range from 2 to 17 Mc/sec/atm and at several temperatures from 23° to 140°C. All results agree within experimental error with the classical values calculated from the viscosity and thermal conductivity of the mixtures plus the effect due to diffusion as computed from the Kohler expression [Ann. Physik 39, 209 (1941)]. Transport properties alone appear to govern sound attenuation in such mixtures under the conditions studied. The total attenuation increases at first as the mole fraction of either of the components increases from zero to a certain value and thereafter decreases, the maximum occurring at a helium mole fraction of between 0.50 and 0.60. However, the relative (percentage) contribution of diffusion, which for the same mole fractions of the components is almost constant with respect to temperature, is greatest at the high mole fraction of helium. For each mole fraction, the total attenuation increases with temperature, but the mole fraction at which maximum attenuation occurs does not vary appreciably with temperature.
Ultrasonic Determination of Viscosity and Rotational Collision Number of High Temperature
Authors: Carnevale E. H. , Lynnworth L. C. , Larson G. S.
Published: September 2005

An ultrasonic (Mc/sec) pulse technique has been used in determining the viscosity of monatomic gases and the rotational collision number of diatomic gases as a function of temperature. The gases studied were argon, helium, nitrogen, and oxygen. The temperature range for all gases was 300°–1300°K, with additional measurements in argon and nitrogen at about 10 000°K. The viscosity has been compared with other experimental data and calculations. The rotational collision numbers have been compared with the theory of J. G. Parker (1959). A discussion of the experimental method and results is presented. [Research supported by the National Aeronautic and Space Administration.]
Acoustic Implications of Persistent Microbubble Model
Authors: Kaizen M. D. , Turner W. R.
Published: September 2005

A model for the persistent microbubble was presented previously [J. Acoust. Soc. Am. 36, 1009 (1964)], the hypothesis being given that the bubble is stabilized by minute particles picked up on the bubble surface, which compress upon out-diffusion of gas to form a wall capable of supporting the hydrostatic pressure, permitting the bubble internal pressure to drop to that of the gas dissolved in the liquid, thus equalizing boundary diffusion and supplying the mass necessary to neutralize buoyancy. The additional stiffness and mass of the compressed wall should affect the microbubble resonant frequency and damping constant. The wall's nonlinear elasticity may be a predominant factor affecting the acoustic cavitation threshold. These implications are explored and applied to several examples of recent experimental evidence.
Cortical Vestibular Projection in the Cat
Authors: Milojevic Bosko
Published: September 2005

Cortical representation of the vestibular nerve has been a problem for the neurophysiologist, since there are no anatomic proofs of the labyrintho-cerebral pathways. Physiological observations of the vestibular influence on the cerebral cortex are far from unanimous. However, electrophysiological studies, using evoked-potentials technique, have proven the existence of a cortical vestibular projection. This area has been localized in the temporal lobe, according to different authors. Recently, many others described the vestibular area to be anterior to the first auditory area and posterior to the somatic area, primarily in the anterior suprasylvian an l ectosylvian gyrus. The conclusions are, however, controversial as to the exact size and localization of the cortical center, or centers. and its ipsilateral or contralateral representation. The present investigation was performed on cats anesthetized with α-chloralose, in order to develop a new surgical approach to the vestibular nerve through the vestibule and to eliminate the possibility of propagation of electrical current through the intermediate nerve or auditory fibers. The effect of vestibular-nerve stimulation upon the cerebral cortex was studied ipsilaterally and contralaterally, and compared with findings of other authors.
Békésy Audiometry in Animals
Authors: Lowy K. , Webster J. , Spragg R.
Published: September 2005

While the audiological use of the Békésy audiometer is predominantly based on hearing thresholds for continuous and pulsed tones, its principle permits rather wide applications of interest for the auditory physiologist. The arrangement reported makes use of standard instruments available at a reasonably well-equipped laboratory and permits automatic recording of responses of a wide variety of sound stimuli at preset levels. The audiometer can be activated by the electrical output due to peripheral as well as central activity in anesthetized or awake and unrestrained animals. The method seems promising for physiological studies of masking, recruitment, etc. [Work supported in part by the National Institute of Neurological Diseases and Blindness, National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare.]
Middle-Ear-Muscle Effects in the Rabbit
Authors: Price G. Richard
Published: September 2005

The rabbit is of special interest because (1) its stapedius muscle has been reported to be especially strong and (2) a study using the rabbit would provide information from a species other than the cat. Using a cochlear-potential technique, measurements were made on 10 lightly anesthetized rabbits. Effects (noted on tones ranging from 0.1 to 10 kc/sec) elicited by contralateral stimulation appeared as changes in the cochlear potential to a tone. The effects noted were similar to those reported for the cat. The maximum attenuation produced was about 20 dB, the frequencies below 1000 cps were affected most, and the amount of attenuation produced increased with increasing intensity of the eliciting tone. [Work supported by grants from the National Institute of Neurological Diseases and Blindness, National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare, and was aided also by a contract from the U. S. Office of Naval Research and by Higgins funds allotted to Princeton University.]
Attenuation of Acoustic Energy Propagating in the Ocean
Authors: Bakhru K. , Berman A.
Published: September 2005

The absorption coefficient of sound in sea water is a function of temperature, pressure, and salinity. In the study of multipath wave propagation of sound in the ocean, the above variations in the parameters of the medium result in the spatial variation of the velocity of sound as a function of depth. For a fixed distance between the source and the receiver in such a medium, the acoustic attenuation will be critically dependent on the particular ray path that the energy travels. This effect of differential attenuation among the various arrivals of a signal through different paths has actually been observed experimentally. Using the empirical formula for the absorption coefficient of sound in sea water proposed by Schulkin and Marsh and a ray-tracing program proposed by the authors for the study of long-range propagation of acoustic energy in the ocean, the total absorption suffered by a ray as it travels in such a medium has been calculated as a function of frequency and initial angle of the ray. A discussion of computed and experimentally obtained results is given. [Hudson Laboratories of Columbia University Informal Documentation No. 82. Work supported by the U. S. Office of Naval Research.]