bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Strength Testing of Adhesives and Piezoceramics
Authors: Aproian Peter , Woollett Ralph
Published: September 2005

Equipment has been developed for testing the strength of adhesive bonds between ceramics and metals and of the ceramics themselves, under the dynamic conditions which prevail in transducers. A longitudinal half-wave resonator with the ceramic sample located at its center is used to develop the dynamic stress in the adhesive and ceramic. The stress level is raised until destruction occurs. A number of methods for measuring the stress were evaluated, including capacitive probes, strain gauges, piezoelectric gauges, motional impedance methods, and an optical interferometer. The bonding of piezoceramic disks was investigated with a solid rod resonator, and piezoceramic rings were similarly investigated in a metal tube resonator. Several epoxy cements and a cyanoacrylate monomer were included in the adhesive tests. The epoxy bonds were often stronger than the ceramic, and the ceramic commonly failed in the stress range 2000 to 4000 psi. Other variables investigated included the adherence of silver electrodes, cleaning procedures, and the effect of cement thickness and ceramic thickness.
Interaction between Ultrasonic Waves at an Imperfect Adhesive Bond in Solid Media
Authors: Lawrie William E.
Published: September 2005

The adherence to a metal surface of a flame-sprayed ceramic coating is related to the acoustic attenuation introduced by interfacial contact. A ceramic-metal bond is formed between two rods each a quarter wave in length. The composite structure is excited by a magnetostrictive transducer and forms a half wavelength vibrator longitudinally resonant at 14 kcps. Alternating stresses of about 250-psi peak are developed at the ceramic-metal interface. Simultaneously, a pulsed 7-mcps sound beam is propagated through the cyclically stressed bond using pulses triggered at different phases of the low-frequency stress signal. Acoustic transmission of the high-frequency pulses is determined as a function of instantaneous low-frequency stress. Variations in received pulse amplitude indicate that transmission through an imperfect bond is a nonlinear function of stress. A continuous high-frequency signal becomes modulated by the low-frequency stress wave on account of the stress-attenuation relation. Approximately 20% modulation is produced with 200 psi peak stress. The percentage modulation is also dependent upon the position of the bond relative to the nodes of a high-frequency standing wave obtained with continuous high-frequency energy. By measuring intermodulation, rather than attenuation, indications of bond continuity are obtained independent of the method of coupling used for the high frequency transducers. (Supported by Wright Air Development Division.)
Bubble Transducer
Authors: Sims Claude C.
Published: September 2005

A new technique for economically producing relatively high-level steady-state sound in water at low frequencies is described. The transducer consists of a conventional low-impedance electrodynamic driver with an air-filled rubber membrane, or “bubble,” over the diaphragm. The system at resonance produces large volume displacement of the water with small linear diaphragm displacement. The theory of operation, physical equipment, and measured results are given.
Dispersive Ultrasonic Delay Line
Authors: Fitch Arthur H.
Published: September 2005

An ultrasonic delay line having a frequency-dependent delay is described. The variable delay is obtained by operating in a dispersive mode of propagation of elastic waves in solids having prescribed symmetry. By a suitable choice of the operating frequency and dimensions, it is possible to obtain an approximately iinear delay-vs-frequency characteristic. In the frequency range up to about 2.5 Mc the midband insertion loss for such a delay line is about 5 to 7 db plus 0.1 db per ft per Mc.
Dispersion and Attenuation of Elastic Waves in a Cylindrical Bar
Authors: Zemanek J. , Becken R. G. , Rudnick I. , Leonard R. W.
Published: September 2005

In the interests of determining the complex elastic constants of a given material (aluminum alloy) over a wide frequency range, the frequency and Q of a large multitude of overtones of a long (3-m), thin (12-in. diameter) bar were measured. These include the longitudinal mode and torsional mode. The frequency range covered was from about 0.5 kc to 100 kc. The elastic constants λ and μ are found to be relatively independent of frequency. The dispersion curve is in reasonable agreement with the Pochhammer-Chree equations for an infinite bar. The Q of the longitudinal mode decreases from about 260 000 at the lowest frequency to 140 000 at the highest.
Dispersion of Flexural Waves in a Cylindrical Bar
Authors: Zemanek J. , Rudnick I. , Leonard R. W.
Published: September 2005

The first 260 flexural modes of a long (3-m), thin (1.25-cm) aluminum bar were measured. The frequency range covered was from 6 cycles to about 105 000 cycles. Comparison of the experimental dispersion curve is made with the Pochhammer-Chree equations for an infinite bar. The dispersion curve is in reasonable agreement with the Pochhammer-Chree theory. Normal modes computed by a modified Timoshenko theory for a finite bar are compared to the experimental resonant frequencies, and reasonable agreement is obtained.
Theory of Reflection and Transmission of Discrete Frequency Sound in Ducts Carrying a Compressible Flow
Authors: Powell Alan
Published: September 2005

Previously the propagation of a plane pressure pulse along a variable duct carrying a compressible flow was discussed in terms of multiple reflections arising from elementary changes of Mach number along the duct [A. Powell, J. Acoust. Soc. Am. 31, 1527–1535 (1959)]. Particularly. it was shown for what Mach number variations the total reflection could be represented adequately by summation of only first-order reflections. That theory is now extended for the case of plane sound waves of discrete frequency: consequently, the time of arrival of the elementary reflections at the end of the duct becomes of primary importance, and the nature of the total reflection is dependent upon the Mach number variation along the duct. Analytical results are so complex that a closed form solution might be possible only for ducts of very particular shape; but some useful approximations are indicated. A more general step-by-step numerical procedure is also described, some typical results being conveniently displayed in Argand diagram form, The transmission characteristics, other than simple amplitude changes, depend upon the double summation of second-order reflections, easily achieved on a digital computer. The method is readily adapted to random noise, provided the wavefronts are plane. (This work has been partially supported by the Office of Naval Research, U. S. Navy.)
Laminar Jets: Physical Sensitivity and Instability Theory
Authors: Powell Alan
Published: September 2005

A laminar jet of fluid is “sensitive” if disturbances from ordinary sound waves are amplified to a macroscopic scale. Relevant hydrodynamic instability theories concern spatial disturbances of hypothetical nonspreading laminar jets. The neutral stability curve by Curle has a ⊂-shape on a Reynolds number-wave-number plot. Difficulties arise in quantitative applications to the real jet, mainly from (a) the essentially temporal disturbances, (b) varying local Reynolds and Strouhal numbers due to jet spread (especially at low values), and (c) transitional velocity profiles. The last two appear to promote increasing stability away from the orifice (except at very small Strouhal numbers). The phenomenon is nonlinear (or quasi-linear at best), fundamentally depending upon (i) Reynolds number, (ii) Strouhal number, (iii) nondimensional disturbance amplitude, (iv) initial velocity profile. In recent experiments by L. D. Miller, R. C. Chanaud, and the author, which are discussed in detail,. (iv) was made invariable; the remaining three parameters were used to establish dynamical similarity for the verge of sensitivity corresponding to the important upper ⊂-limb. Expectedly, parameter (iii) is significant. Further developments will concern the lowest Reynolds number limit and the lower ⊂-limb, where the phenomenon is a little more obtuse. (This work has been partially supported by the Office of Naval Research, U. S. Navy.)
Electronic Organ Ensemble by Means of “Optimum Generator Utilization.”
Authors: Meyer Albert
Published: September 2005

“Optimum generator utilization” is a method of distributing the outputs of a number (G) of continually oscillating generators to a number (S) of stops, with G<S, in such a way that the most likely stop combinations will derive from the greatest number of generators.
Panoramic Tone Enhancement System
Authors: Bissonette A. J. , Brombaugh J. B. , Jones E. M.
Published: September 2005

The Panoramic Tone system is a new means for enhancing electrically produced or reproduced sound. Organ music has traditionally been heard in environments with long reverberation times. Therefore, it is desirable from a musical standpoint for this effect to be present in the sound produced by electronic organs played in homes and small churches. The heart of the new system is a long wire equipped with an electromechanical transmitter and receiver at its ends. Multiple reflections and termination losses control the properties of the tonal enhancement. The wire is coiled into a helical shape only for convenience in packaging. The sound transmitted along the wire has been translated to the ultrasonic frequency range. This greatly attenuates any disturbance from noises and shock at audible frequencies. It also gives a more uniform trend for the response-frequency characteristic and the reverberation time-frequency characteristic than other methods have provided.
Electroacoustic Tone Source Extending into the Infrasonic Range
Authors: Duncan R. K. , Stein J. L.
Published: September 2005

Measurements were made on the low frequency tones radiated from a very large pipe organ. In the purer stops, such as the contra bourdon, the first partial predominates, even in the C0-C1 octave (16–32 cps). This indicates that an electroacoustic tone radiating system for electronic organs should be capable of radiating fundamental tones as low as 16 cps. Such a system is demonstrated and described.
Specification of Loudspeaker Characteristics
Authors: Kaye David H. , Klepper David L.
Published: September 2005

This paper discusses loudspeaker characteristics which must be published by the manufacturer in order for the acoustical engineer to intelligently design a given loudspeaker system as part of the room acoustics design. It considers those characteristics of cone-type direct radiator loudspeakers, column loudspeakers, and horn-loaded loudspeakers most important to typical distributed and central loudspeaker systems. Reasons are given for preferring continuous pure-tone measurements to measurements using bands of noise, square waves, etc., and for preferring anechoic or “free-field” measurements to so-called “typical-room” measurements. Errors in sound-system design that can result from a lack of information or from misinformation are discussed.
Semiconductor Strain Gauges
Authors: Thurston R. N.
Published: September 2005

The relatively large piezoresistance coefficients relating resistance change to stress in certain semiconductor single crystals make them potentially attractive as sensing elements for the measurement of strain, force, torque, acceleration, etc. The use of not only longitudinal, but also transverse and shear effects will be illustrated. The response of some of the more promising materials will be reviewed and the special features of certain particular orientations will be discussed.
Effect of Noise Correlation on the Masked Threshold for Tone
Authors: Robinson Donald E. , Jeffress Lloyd A.
Published: September 2005

This is a repetition and an extension of a study of the effect of the interaural correlation for a masking noise upon the masked threshold for a 500-cps tone, reported in 1953 by Jeffress, Blodgett, and Deatherage. We failed at that time to realize that an uncorrelated noise can produce a masking level difference (MLD), and used the homophasic condition, at each value of the correlation, as the reference level for computing MLD's. In the present study the results are presented as signal-to-noise ratios based on the effective level of the noise. They show, as the results of the earlier study did, a very rapid increase in masking as the correlation is reduced from unity. The change is not, however, as rapid as that associated with the reduction of the autocorrelation for the critical band of noise when a time delay is introduced into the noise channel to one ear. The paper will discuss some of the implications of this fact for hearing theory.
Masking of Pulsed Tones by Bands of Noise
Authors: Small Arnold M. , Campbell Richard A.
Published: September 2005

If, for instance, a 2200-cps tone is pulsed 150 times/sec, a low pitch (periodicity pitch) will be heard corresponding to that of a 150-cps pure tone. This experiment investigates the effectiveness of different bands of filtered noise in the masking of such pulses and in the masking of two pure-tone stimuli, 150 and 2200 cps. Although the pulses and 2200-cps pure tone yield quite different pitches, the present results indicate that the masking of each requires nearly identical frequency components and sound levels of noise. The 150-cps tone, although yielding a pitch approximating that of the pulses, requires greatly different characteristics of noise to mask. Considering differences in apparatus and technique, reasonable agreement with other studies of pure tone masking by bands of noise is found. If masking is viewed as a neural phenomenon, these data provide additional evidence of the neural nature of periodicity pitch.
Backward Masking: Binaural and Monaural Conditions
Authors: Elliott Lois L.
Published: September 2005

“Backward masking” is the term used to denote the situation in which one auditory stimulus is masked by another auditory stimulus which follows it in time. This study investigates backward masking for both the monaural condition (masked tone and masking noise presented to same ear) and the binaural condition (masked tone and masking noise presented to opposite ears). Experimental conditions included a 50-msec white noise masking signal presented at 70 and 90 db re 0.0002 d/cm2. The 1000-cps probe (masked signal) was presented at 5- and 10-msec durations and was varied in intensity to locate the masked threshold. Offset of the probe tone preceded the onset of the masking noise by time intervals ranging from 0 to 50 msec. On every trial a “standard” burst of noise, identical to the masking noise, was presented for comparison. Eight subjects participated in the randomized block designed experiment. Results indicate monaural backward masking occurs over masking intervals as long as 25 msec. In contrast, binaural backward masking occurs for intervals as long as 15 msec. The shapes of the two sets of backward masking curves differ considerably with the monaural condition showing considerably more masking at short masking intervals than the binaural condition. Corresponding results for monaural and binaural forward masking are presented. The significance of the results for auditory theory is considered.
Acoustics, Committees, and Information
Authors: Colton Ernest
Published: September 2005

The specialized type of meeting suscitated by committees are described. Suitable models for typical committees are indicated. The acoustic limitations defined by each model are noted. It is concluded that committees would be among the least efficient ways of conveying and interchanging any possible information carried by sound waves, even in acoustically ideal environments.
Guided-Wave Dispersive Delay Lines
Authors: May John E.
Published: September 2005

A variety of new delay devices having delay times which are functions of frequency have been developed. These devices are based on waveguide propagation of ultrasonic waves in solid rectangular strips or circular wires. In contrast to the usual delay networks composed of many electrical sections, these dispersive delay lines are less expensive, occupy less space, and provide smoother delay characteristics. A linear delay network has the property that it transforms a short AM pulse into a long FM pulse. This makes possible the design of radar systems with increased range without requiring a corresponding increase in peak power. Existence of an inflection point in the delay versus frequency characteristic of the lowest longitudinal mode in a strip or a wire makes possible delay lines having an approximately linear delay characteristic. A typical example is a delay line operating in the lower megacycle region which has a product of time variation times bandwidth equal to about 100. Delay lines having various types of curvature can be designed by utilizing certain longitudinal, flexural, or shear modes in wires or strips.
Applications of Delay Lines in Correlation Processing
Authors: Hoover C. W.
Published: September 2005

Correlation-processing techniques for recovering information from a signal contaminated by noise are being used very fruitfully today in fields ranging from radar to medicine. Processing of this type allows us to make use of a priori information which we may have, or of the results of repeated observations. Our ability to use a priori information or repeated experiments is in general limited only by the number of degrees of freedom or the time-bandwidth product of the correlator. This paper discusses: (1) the general principle involved in correlation processing, (2) a variety of correlators which are based upon delay lines and (3) two interesting applications, one in medicine and one in radar. In conclusion, a chart is shown which summarizes in a time-band width plane plot, the characteristics of most of the delay-line correlators known to the writer. This diagram shows regions where improvements in the technology will be of immediate profit in information processing applications.
Wide-Band Variable Ultrasonic Delay Line
Authors: Price O. R. , Pedinoff M. E. , Lax E. , Sittig E. , Crane G. R. , Duval R. H.
Published: September 2005

An ultrasonic delay line has been developed which employs water as the delay medium and permits continuous adjustment of delay between the limits of 28 and 58 μsec. Adjustment of delay is effected by movement of a corner reflector relative to two crystal transducers whose positions are fixed. The center frequency is 30 Mc and the bandwidth is in excess of 10 Mc. Uniformity of bandwidth and response over this range is controlled by a combination of measures including selection and design of backing and bonding materials, offsetting the resonant frequency of the transducers from the operating band and use of particular alignment techniques. Delay stability is achieved by operating the unit at the inversion temperature of sound in water. The design features of the unit as well as water. The design features of the unit as well as the electrical characteristics of the system are discussed.
Ultrasonic Delay Lines for Digital Data Storage
Authors: Meitzler Allen H.
Published: September 2005

This paper describes the design features and performance characteristics of a delay line design which is specifically intended for digital data applications. The design consists basically of a delay medium in the form of a long, thin strip with piezoelectric ceramic, thickness-shear mode transducers bonded to the end faces. The strip acts as an elastic waveguide in which the energy contained in an input elastic pulse is propagated by a number of modes with varying amounts of dispersion. By the proper use of absorbing material along the edges of the strip, it is possible to suppress selectively the more dispersive modes and thereby reduce the width of the output pulse to the extent that megacycle bit rates may by used even in lines with delays of the order of 10 msec. Since the medium acts as a waveguide, long delays may be obtained at relatively low loss. In a typical design, to be described in detail, the line has a delay of 4.3 msec, an insertion loss of 34 db, and a maximum bit rate (on a nonreturn-to-zero basis) of 2.5 mc. In addition to the advantage of low loss, other advantages associated with the fact that the delay medium acts as a waveguide are (1) the elimination of spurious signals due to beam spreading, and (2) the ability to coil the strip into a tight spiral which, in turn, makes possible compact assemblies with long delay times.
Synthesis of Dispersive Delay Characteristics by Thickness Tapering in Ultrasonic Strip Delay Lines
Authors: Fitch A. H.
Published: September 2005

Tapering the thickness of a dispersive strip delay line operating in the first longitudinal mode can yield a variety of delay characteristics unobtainable with strips of uniform thickness. A strip whose thickness varies in some manner along its length may be thought of as a number of strip sections of constant thickness in series. The additive delay of these series sections can produce an over-all delay characteristic completely different in form from the delay characteristics of the individual sections. A design procedure involving the methods of linear programming has been developed which allows a unique determination of the taper required to produce a given delay function. Performance data is presented for several delay lines designed to approximate both linear and nonlinear delay-vs-frequency characteristics.
Dependence of the Lowest Thickness Longitudinal Mode Resonant Frequencies of Long Rectangular Bars on the Width and Thickness Dimensions
Authors: Meeker T. R.
Published: September 2005

A first-order theory of the dependence of the lowest thickness longitudinal frequency constant (ft) of long bars on width to thickness ratio (w/t) is proposed. The essential idea of this theory is that the frequency constant (ft) of long bars is a function of the width for w/t less than 1 and that (w/t) (ft) is a function of the thickness for w/t greater than 1. The dependence of the frequency thickness product on the dimensions in each case is the same as the velocity of the lowest longitudinal elastic mode of the infinite plate on the plate thickness. Experimental resonant frequency measurements on long bars of three ceramic transducer materials, namely, barium titanate, lead zirconate titanate, and sodium potassium niobate, are compared with those calculated from the proposed theory for values of w/t from 0.2 to 6.0. The fit between experiment and theory is optimized by a suitable choice of isotropic elastic constants for the resonator. These “best fit” values of the elastic constants are then compared with the values found by the usual methods. In this way, it is shown that the proposed theory is consistent with the dependence of the lowest resonant frequency of the bar on the dimensions and the elastic constants. The application of the theory to a method of determining both isotropic elastic constants using the thickness longitudinal mode resonant frequencies of long bars with finite widths and thicknesses will be described.
Irregular Atlantic Sound Velocity Profiles
Authors: Lord N. W. , Berman A. , Sherry H. B.
Published: September 2005

The variation of sound velocity with depth was intensively studied at several locations in the Atlantic Ocean connected with the sound-transmission experiment of the accompanying abstract (F2). The sound velocity was measured instantaneously in situ with a sing-around type meter of NBS design. The depth was also measured instantaneously by timing the travel of the fathometer sound pulse to a connected hydrophone. For the two receiving stations NNE of Barbados, time instabilities and variation with depth of the sound velocity were statistically similar. At a given depth in the sound channel (2.5–4.0 thousand feet) the velocity varied randomly in time with excursions of a few feet per second occurring with periods of a few minutes. For measurements placed 50–100 ft apart in depth the velocity varied irregularly again to the extent of several feet per second while tracing out overall a very flat sound channel bend. This can be looked at as a randomly time-dependent multi-channel structure which gives rise to a defocusing and perhaps scattering of the ideal sound channel transmission. This effect will be exhibited using the results of ray calculation for several idealized profiles of graded irregularity. (This work was supported by the Office of Naval Research.)
Effect of Tidal Currents on 25 cps Shallow Water Ambient Noise Measurements
Authors: Willis Jack , Dietz Frank T.
Published: September 2005

With the support of the Office of Naval Research, 1400 measurements were made during March, 1961, of the ambient noise in a one-octave band centered at 25 cps, using a bottom-mounted three-axis seismometer situated in a shallow water location in Narragansett Bay, Rhode Island. No pronounced differences were observed among the outputs of the three geophones. Acoustic data and environmental information including wind speed, wind direction, wave height, and tidal data were linearly correlated by electronic computer. The results show that significant correlations exist between the ambient noise and the wind speed, wave height, and the time derivative of the tidal level curve. The latter factor, a measure of tidal current, has a marked association with the sound level and is correlated with changes of the order of 25 db. Both lunar and solar tidal effects were detected. Recent preliminary data obtained with the seismometer buried in the bottom indicated that the greater part of the sound-level variation can be attributed to flow noise around the receiver.
Study of the Bivariate Distribution Function of Ocean Noise
Authors: Green A. H.
Published: September 2005

It is generally assumed that ambient ocean noise can be represented as a gaussian process. The work reported here considers some second order amplitude distributions to attempt at least partial experimental verification of the hypothesis of normality. The data consisted of several recordings of ocean noise from which bivariate sample points were taken to obtain empirical distribution functions for different values of time separation. Two statistical methods are employed. The first utilizes the chi-square goodness of fit test, and the second compares the third and fourth order sample moments to the corresponding moments of a known second order distribution function. Best estimates of the mean and variance of each variate and the correlation coefficient of the variates have been obtained for each sample. Each of the methods will be described and the results and conclusions will be discussed. (This work was supported by the Office of Naval Research, U. S. Navy Department.)
Hydrodynamic Noise Reduction
Authors: Silverman Murray H.
Published: September 2005

The reduction of hydrodynamic noise resulting from singing and cavitation was a serious problem in a recent wire-guided high-speed underwater missile development. The noise level of this body not only was sufficiently high to prevent a model of the latest developed sonar from tracking other bodies, but permitted a possible enemy more than sufficient time for successful evasion. The principal noise sources originated from both cavitation and the singing of the missile fins and two counter-rotating propellers. To eliminate the propeller singing, wedges of 40°, 33°, and 25° were applied to the propeller's trailing edges. Only the 25° and 33° angles successfully eliminated the propeller singing. Sanding the critical area of the fins, theoretically determined from the Strouhal number K = fd/v, where f is the frequency, d the body's trailing edge diameter, v the fluid velocity, and K is a constant, eliminated the fin singing without noticeably increasing the cavitation noise level. However, a commercial process was required. Roughening the critical area by sand blasting, or use of a painted, crackle-like finish were unsuccessful. Wedging with an apex angle of 25° succeeded. Flow noise also appeared to be reduced by eliminating cracks, voids, and rough areas. The data obtained also implied that singing (i.e., the Strouhal number) may not be so much a function of the trailing edge depth and its vertical thickness as it is of an effective depth or area forward of this point.
Voice Communication in Aircraft and Aerospace Systems
Authors: Veneklasen Paul S.
Published: September 2005

As the boundaries of man's missions above, around, and beyond the earth enlarge into unlimited space, new problems are presented in voice communications. The solutions to these problems are essential to the continued effectiveness of man in military aircraft and spacecraft. Man will be an essential and controlling factor in the space environment, and his usefulness and effectiveness there will be, as in all his historic past, utterly dependent upon communications: language, voice, and hearing, received and transmitted. Missions near the earth will be of shorter duration, higher speed, and higher noise level. Space missions will probably be less noisy, but their duration will make the 40-hr limit appear as a moment. Extreme discomfort associated with communication equipment has critically hampered the operational effectiveness of flyers on long range missions. We must discover new transducers which will permit reduction in the encumbrance of combined communication, protection, and respiration equipment worn by flyers during high altitude, long range missions. The noise field largely determines the possible techniques for speech projection and reception. The existing and prospective noise fields for aircraft communications are reviewed. Both projection and reception systems consist of a transducer, a coupling means from transducer to voice or hearing, and a noise exclusion device. A morphological chart of available devices and techniques is given. Criteria are described for evaluation of the effectiveness of a transducer system, involving not only advanced psychophysical parameters of speech intelligibility, but also equivalent physical factors peculiar to flight communication in high ambient noise. Evaluation of encumbrance or wearability in terms of long-term pain tolerance greatly needs quantitative procedure. New transduction techniques are described and compared with conventional methods to illustrate the state of the art and the problems and prospects for future advancement.
Bandwidth Compression of Speech by Spectrum Sampling
Authors: Kryter Karl D.
Published: September 2005

An experimental communications system has been built that filters speech into a number of narrow bands. The width of the bands, at the 3-db downpoints on the filter skirts, can be set at 25, 50, 100, 300, or 500 cps; the positions of the center frequencies of the filters are variable. A number of tests were conducted of the intelligibility of speech transmitted over a wide variety of combinations of filters having different bandwidths and different center frequencies. A few listening tests also were made of the effects on intelligibility of sequentially sampling in time the output of the various narrow band filters. The results of these tests show that intelligibility is a joint function of the number, width, and position on the frequency scale of the narrow passband filters. The most efficient combination of filters we have found to date, in terms of total effective bandwidth required for 80% PB word intelligibility, consists of five filters each 100 cps wide measured at the 3-db downpoints on the filter skirts. This represents a bandwidth saving over a low pass system (simulated telephone) by a factor of about 3 or 4 to 1; we previously reported [J. Acoust. Soc. Am. 32, 547–556 (1960)] a bandwidth reduction of 2 to 1 with three filters having bandwidths of 500 cps. (This work was performed under contract with the U. S. Army Signal Research and Development Agency.)
A Print-Out System for the Automatic Recording of the Spectral Analysis of Spoken Syllables
Authors: Olson Harry F. , Belar Herbert
Published: September 2005

A print-out system has been developed which automatically records any one of over a trillion different quantized analyses of a spoken syllable. The main purpose is research toward improved methods of recognizing speech by machines. However, other applications for the digitized transmission of speech also are indicated. Results of tests made are analyzed and different approaches to the decoding problem are presented.
Articulatory Analog of the Vocal Tract and Nasal Cavities
Authors: Hecker M. H. L.
Published: September 2005

A modified version of the dynamically controllable electrical analog of the vocal tract [G. Rosen, J. Acoust. Soc. Am. 30, 201–209 (1958)] that includes a recently developed analog of the nasal cavities is described. The acoustical coupling between the vocal tract and the nasal cavities is electronically varied in the same way as the effective cross-sectional area of each section making up the transmission line representing the vocal tract. Formal listening tests have been conducted to determine the most suitable vocal-tract configurations for the production of nasal consonants in consonant-vowel and vowel-consonant syllables. Other listening tests have determined the most suitable patterns of temporal variables for the production of these syllables. In general, it is found that more natural-sounding syllables are obtained when the velopharyngeal coupling varies slowly with time compared to changes in the configuration of the vocal tract. The results compare favorably with cineradiological data recently reported and are interpreted to support the point of view that studies of the performance of an articulatory synthesizer reveal important details concerning the production and perception of natural speech. The experiments demonstrate that speech can be synthesized from articulatory information in a straightforward and natural manner. (This work was supported in part by the U. S. Army Signal Corps, the Air Force Office of Scientific Research, and the Office of Naval Research; and in part by the Air Force Cambridge Research Laboratories and the National Science Foundation.)
Articulation Testing at High Speech Rates
Authors: D'Eustachio D. , D'Eustachio I.
Published: September 2005

At the October 1960 meeting of the Acoustical Society of America we reported that articulation scores are a function of the rate at which material is presented to the listeners. The phonetic alphabet used was not designed for fast writing, and the listeners had difficulty transcribing at rates faster than 30 CVC syllables a minute. In an attempt to reach normal speech rates (six non-redundant speech sounds a second) a new testing crew has been trained, using an improved alphabet. Rates exceeding 50 CVC syllables a minute have been possible. The scores continue to fall as the rate increases. It also has been observed that the test becomes more discriminating as the rate increases. For example, in comparing a high quality speaker (lent to us by Bell Telephone Laboratories, Inc.) with live speech, scores are alike at 40 syllables a minute but show a significant difference in favor of live speech at 50 syllables a minute. Also, at the high rates absolute performance but not relative performance appears to depend critically on training. Training techniques will be discussed.
Interference in Reflections from the Ocean Bottom and Subbottom
Authors: Brown M. Vertner , Ricard James
Published: September 2005

A strong interference pattern has been observed in the reflection of monochromatic pings from the ocean bottom. The experiment was performed in the Gulf of Mexico at 24°16′N, 85°15′W. The acoustic pings had a frequency of 120.5 cps and a length of 0.12 sec and were repeated every sec. The transmitter was at a depth of 75 ft and the receiver at 3000 ft. The energy in successive reflections varied by as much as 6 to 1 with a mean fluctuation of 30%. This rapid change of level corresponds to that observed in the “direct” arrival which, because of the shallow source, is due to the superposition of the truly direct and the surface reflected arrivals. This is probably the principal cause of the short-term fluctuations in the bottom reflections. When these reflections are averaged in groups of ten, one obtains a moderately smooth relation between energy and range which exhibits a pronounced interference structure. This gross pattern is not due to the surface interference. The pattern observed can be interpreted in terms of a 43-ft layer having a velocity of 6280 ft/sec. (This work was supported by the Office of Naval Research.)
Seismic Reflection Measurements in the Grenada Trough
Authors: Clay C. S. , Northrop J. , Sherry H. B.
Published: September 2005

A vertical array of deep hydrophones was used to monitor reflections from shallow shots in the Grenada Trough. The records show that the first bottom reflection undergoes a change in the direction of first motion at an incident angle of 77 deg. This change in phase indicates a bottom velocity less than water and when substituted in the equation presented by Fry and Raitt (1961) gives a bottom velocity 2.5% less than the bottom water velocity of 4975 ft/sec. Analysis of subbottom reflections also indicates a low velocity bottom layer about 170 ft thick underlain by a 660-ft thick layer of 8800 ft/sec material. The low velocity sediment would be masked in refraction shooting and indeed has not been detected on refraction profiles in the Trough. (This work was supported by the Office of Naval Research.)
Ocean Basin Structure as Revealed by Seismic Profiler Studies
Authors: Ewing John , Ewing Maurice
Published: September 2005

A new technique for making continuous reflection profiles in the oceans has been developed in which reflection shots are recorded in a manner analogous to that employed in standard echo sounding equipment. This provides automatic correlation and integration of arrivals and makes possible rapid examination and analysis of large volumes of data. During recent months, several thousands of miles of track, mostly in ocean basin areas, have been studied with the Seismic Profiler. The deepest reflector seen in the Profiler records is the upper surface of a layer with seismic velocity 4.5–5.5 km/sec. This reflecting surface is very uneven. In large areas of the ocean basins, it is almost entirely devoid of sedimentary cover, except in pockets, and its roughness is accurately expressed by the sea floor topography. In other areas, principally in the abyssal plains and on the continental rises, the relief in this layer is no different, although it is obscured by up to a few kilometers of flat lying sediments. A prominent reflector within the sedimentary column is seen throughout the latter areas, usually at a depth of about 400–500 m below the sea floor. Its smooth, flat surface which is comparable to the present sea floor in abyssal plains, indicates that turbidity current deposition has long been the dominant process in deep sea sedimentation. The universal roughness of the top of the 4.5–5.5 km/sec layer and the absence of reflections from beneath it are taken as evidence that the layer is part of the original oceanic crust, possibly a less dense differentiate of the crustal material. This opposes the view held by some that the layer consists of older sediments, possibly covered by lava flows.
Measurements of Absorption Coefficients on Plates
Authors: Heckl M.
Published: September 2005

A method equivalent to the reverberation chamber method of architectural acoustics was used to determine the absorption of vibratory energy at the connection of plates to substructures. The applications and the limitations of the method are discussed. Experimental results obtained on typical constructions show that some supporting substructures have an absorption whose frequency dependence is governed mainly by their geometries. Absorption may be accounted for by frictional and viscous losses at the substructure. As pointed out in the previous papers the results are of some interest for the calculation of the vibration of structures excited by sound fields. They also can be used to find the average response of systems excited by point forces. (Supported by Aeronautical Systems Division, Air Force Systems Command, U. S. Air Force.)
In-Place Flexural Damping of Walls
Authors: Watters B. G.
Published: September 2005

Several physical properties of the materials from which walls are constructed are important to the transmission loss. For single walls, the surface weight, bending stiffness, and internal damping factor are generally important. When a wall is erected either in a building or in a testing laboratory, some additional physical properties are added which can influence the transmission loss. One of the most important of such properties is vibrational damping for flexural waves arising from conditions at the edges of the panel. The importance of such edge damping is considered. Measured laboratory and field data of in-place damping are presented.
Field Sound Transmission Loss Tests of Movable Partitions for School Classrooms
Authors: Bonvallet G. L.
Published: September 2005

Field sound transmission loss tests have been made on a number of movable partitions installed in the Chicago Laboratory School of the University of Chicago on an experimental basis. Installation and tests were supported by the Educational Facilities Laboratories, Inc., New York City, to obtain performance information. Partitions tested included individually movable panels with perimeter seals, accordion folding units, and a new, heavy curtain type incorporating woven lead thread. A 6-in. lightweight aggregate concrete block wall was included for comparison. Results indicate a range of performance from satisfactory to inferior for the purpose. The nine-frequency average of both noise reduction and sound transmission loss do not, however, rank order the units ia agreement with subjective judgment.
Effects of Masking upon Lateralization of Cophasic and Antiphasic Clicks
Authors: Flanagan J. L. , David E. E. , Watson B. J.
Published: September 2005

At the last meeting of the Society [J. Acoust. Soc. Am. 33, 840(A) (1961)], we described an experiment to measure the interaural time difference for binaurally lateralizing cophasic (rarefaction-rarefaction) pulses, and antiphasic (rarefaction-condensation) pulses. High-passed masking moise, with cutoff frequency fc, was used to cause the coherent neural information to originate in the apical half of the basilar membrane. The disparity in interaural times for lateralizing cophasic and antiphasic conditions was explicable in terms of (in fact, predicted by) the calculated displacements of the basilar membrane. Principal cophasic fusions of the sound image were made for zero interaural time. Principal antiphasic fusions, on the other hand, were made for a lead of the condensation pulse by a time approximately equal to 12fc sec. Using the procedure previously outlined, we have extended the experiment to the complementary situation where the significant neural information is constrained to originate from the basal portion of the membrane. To this end, low-passed masking noise is used with cutoff frequencies of 600, 1200, and 2400 cps. Again, the principal cophasic fusions are found for interaural times which are nominally zero. The principal antiphasic fusions, however, are now made for interaural times which are nominally constant at about 200–400 μsec, and with condensation lead. As before, computations from a mathematical model [J. Acoust. Soc. Am. 32, 1494(A) (1960)] show that this result is also explicable in terms of middle-ear transmission and basilar membrane displacement.
Short-Time Aftereffects of Noise on Auditory Nerve Responses
Authors: Peake W. T. , Buoncristiani J. F.
Published: September 2005

Auditory nerve responses to clicks have been recorded from cats by means of a gross electrode placed near the round window of the cochlea. If the clicks are preceded by a burst of wideband noise, the amplitude of the click response is reduced. We have measured the amplitude of N1 as a function of noise-burst intensity IN, noise-burst duration D, time interval between the cessation of the noise and the occurrence of the click T, and intensity IC. The ranges of IN and D were restricted so as to produce aftereffects lasting less than 10 sec. For fixed values of T and IC, a family of values of IN and D can be found which produce equivalent aftereffects on N1. Results show, however, that pairs of D and IN values which are equivalent at one value of T are not equivalent for other values. In particular, recovery to a long, low-intensity burst takes place more slowly than recovery to the “equivalent” short, high-intensity burst. Also, equivalence for a given value of IC does not necessarily imply equivalence for other click intensities. (This work was supported in part by the U. S. Army Signal Corps, the Air Force Office of Scientific Research, and the Office of Naval Research.)
Nonlinear Diverging Waves
Authors: Westervelt Peter J. , Radue Joanne
Published: September 2005

N. W. McLachlan and A. L. Meyers [Proc. Phys. Soc. (London) 47, 644 (1935)] and K. A. Naugol'nykh [Soviet Phys.—Acoustics 5, 79 (1959)] have obtained solutions valid to second order in the wave amplitude for spherically symmetric waves. We have generalized their results and obtained solutions for nonspherically symmetric waves. If the first order density wave satisfying the linear wave equation is taken to be ρ1 = (A/r)e−i(ωt−kr) × f(θ,φ), we find the second-order correction to the density to be ρ2 = −12 iρ0−1kA2r[ln(rr0)][2+c0−2ρ0(d2pdρ2)ρ=ρ0]×e−2t(ωt−kr)f2(θ,φ). This result is subject to the restrictions that kr≫1 and that |∇f| ≪k. This result corresponds to the solution found in the literature for the special case of the spherically symmetric wave, f(θ,φ) = 1. (This work was supported jointly by the U. S. Office of Naval Research and the Aeronautical Systems Division, Air Research and Development Command, U. S. Air Force.)
Steady Flow Boundary Layer in Acoustic Streaming
Authors: Westervelt Peter J.
Published: September 2005

The observed configuration of sonically induced flow in the vicinity of solid objects may depart significantly from predictions based on first-order perturbation theory whenever the acoustic particle displacement amplitude s exceeds in magnitude the acoustic boundary-layer thickness δAC. This change in the flow pattern seems to be intimately connected with two related physical effects: The observed increase in heat transfer from heated objects subjected to intense sound; the observed increase in drag experienced by an object subjected simultaneously to a steady unidirectional flow and to an intense sound field. An attempt is being made to understand these effects by extending the conventional perturbation theory to higher orders, a formidable task unless analytic solutions are available for the first-order perturbations. In connection with an attempt to find analytic solutions for the streaming in the vicinity of a right-circular cylinder, a formula has been obtained for the streaming boundary layer thickness δDC divided by the cylinder radius a, δDCa = [(1 − 13√3 δACa)−12 −1] + [2 − 13√6]δACa. (This work has been supported by the Air Research and Development Command, U. S. Air Force.)