bluuebunny/crossref_metadata_2025 huggingface dataset:
Impedance and Shock Spectra
Authors: O'Hara George J.
Published: September 2005

Attempts to combine shock spectra, by envelope of fiducial limit types of analysis, to produce curves useful for design purposes have led to design shock spectra which are extremely overconservative. It was noticed that this technique assumes that the impedance of any structure at its foundation for its fixed base natural frequencies is very low, and therefore unable to affect the foundation motion. This was in contrast to test evidence that a dip would appear in the regions of these frequencies in the spectrum plot. This paper examines the theory of shock spectra, Fourier spectra, and mechanical impedance to determine qualitatively the effect upon shock spectra of the dynamic reaction of structures. The concept of shock spectrum dip is presented, explained, and experimental verification exhibited. Several theorems regarding shock and Fourier spectra are advanced, and a definition of shock spectrum proposed. The necessary distinction between shock spectrum values at fixed base natural frequencies of a structure and at natural frequencies of a structure-foundation combination is demonstrated. The potentially extreme overconservatism in design resulting from incorrect usage of shock spectra is pointed out.
White Noise Representation of Earthquake Motion in Elasto-Plastic Structures
Authors: Bycroft G. N.
Published: September 2005

This investigation is intended to show that white noise is a suitable representation of earthquake motion in both elastic and elasto-plastic structures. Further, it is suggested that a white noise source used in conjunction with an analog computer is a convenient method of analyzing structures subjected to complex ground motions and of assigning probabilities to the deformations arising.
Current Status of Speed-of-Sound Measurements in Water
Authors: Greenspan Martin
Published: September 2005

Various techniques give results for the speed of sound in water which differ from one another by amounts which exceed the estimated errors. The available results will be reviewed. Possible sources of error will be listed and a program leading to a possible solution of the dilemna will be outlined.
Effects of Progressive Ultrasonic Waves on a Narrow Light Beam Experimental
Authors: Hargrove L. E.
Published: September 2005

An experimental study of slit diffraction of a light beam which is also diffracted by an ultrasonic wave in water is described. The time-average intensity distribution in the broadened source slit image is presented as a function of several parameters. The experimental results are compared with the theoretical results of Zankel. (This research was supported by the Office of Ordnance Research, U. S. Army.)
Light Diffracted by Two Parallel Ultrasonic Waves of the Same Frequency
Authors: Zankel K. L.
Published: September 2005

If light is passed through first one and then another parallel progressive ultrasonic wave of the same frequency, then the optical effects should add vectorially. Procedures based on this principle could be used more accurately to measure properties of ultrasonic wave propagation. The results of passing light through two such waves are discussed. (This work was supported by the Office of Naval Research.)
Some Characteristics of the Noise Produced by Several Contemporary Army Weapons
Authors: Doelling Norman , Kryter Karl D.
Published: September 2005

Measurements of the noise produced by several contemporary Army weapons have been made as part of a larger study of the effects of weapons noise on hearing that is being carried out by the Sound Section of the Army, Medical Research Laboratory at Fort Knox, Kentucky. The study is seeking to discover correlations between noise exposures and the hearing acuity of the exposed personnel. Noise measurements were made in and around a weapons carrier and two tanks, and near personnel during the firing of a 30 caliber M-1 rifle, 30 caliber and 50 caliber machine guns, a 76-mm gun, a 90-mm gun, and a 105-mm howitzer. The noise exposure parameters that have been investigated are (1) acoustical stability of the weapons as noise sources; (2) the rise times; (3) the durations; (4) the peak value of sound pressure level; (5) the spectra of the “integrated” sound pressure; and (6) the distribution of these parameters in and around the weapons. Typical data are presented to illustrate the results which have been obtained. (This work was sponsored by the Surgeon General, U. S. Army under Contract No. DA-49-007-MD985.)
Sound Absorption by Free-Hanging Resistive Sheets
Authors: Bolt Richard H.
Published: September 2005

Absorption, reflection, and transmission coefficients have been derived for a plane wave of sound at an arbitrary angle of incidence on a thin sheet of flow resistance r = R/ρc and specific mass m = M/ρc, freely suspended in anechoic space. At normal incidence, for large ωm, the absorption reaches a maximum of 0.50, which occurs at r = 2. The statistical coefficient (appropriately averaged over angle) exceeds 0.40 over a considerable range of r and ωm. In a room with fully diffused sound, a sheet of dimensions large compared with wavelength, suspended away from room boundaries, introduces a number of absorptive units (sabins) which approaches (at high frequencies) twice the absorption coefficient times the sheet area. Confirming measurements in a reverberation chamber suggest certain configurations of “space sheets” for sound absorption in rooms.
High-Temperature Acoustical Properties of Materials
Authors: Lawrie William E.
Published: September 2005

The normal absorption coefficient and the normal specific acoustic impedance of the following several materials were measured as a function of temperature for temperatures up to 1500°F and frequencies up to 1800 cps. The specific acoustic impedance of all materials measured increased with temperature and caused a variation in absorption which is dependent upon the variation of the specific acoustic impedance of the material relative to the specific characteristic impedance of air. An acoustic impedance tube with the sample holder inserted into an electric furnace was used for the measurements. Both longitudinal and vertical temperature gradients were present in the tube. Empirical corrections were made to the data, but the detailed effect of the gradients on the measured absorptions and impedances has not yet been completely determined. (This research was supported by Wright Air Development Center).
On the Imperfect Problems of Acoustics
Authors: Mawardi Osman K.
Published: September 2005

A thesis is presented to the effect that the approximate formulation of a physical problem bears a remarkable analogy to the performing of a mental experiment. Using the criteria for the evaluation of “meaningful” experiments, variational principles in acoustics are discussed. Several acoustical quantities such as reverberation, time, frequency irregularity, etc., are examined in the light of this analogy.
Random Sound Field in Reverberation Chambers
Authors: Balachandran C. G.
Published: September 2005

The production of random sound fields in reverberation chambers is very necessary for the determination of sound absorption coefficients and sound transmission losses. Various techniques for randomizing sound fields have been proposed in the past. The aim of this paper is to present experimental results comparing the suitability or otherwise of some of the practices of randomizing sound fields, viz., altering the room geometry by a rotating vane, by fixed scattering surfaces on the walls or in space, or by absorbing patches on the walls. To assess the state of randomness of the sound field three methods were used: the correlation coefficient between two observation points, the standard deviation of reverberation time measurements, and the measurement of the sound absorption coefficient of a standard sample.
Acoustical Research Facilities at Columbia Broadcasting System Laboratories
Authors: Bauer Benjamin B.
Published: September 2005

The recently inaugurated Research Laboratories of the Columbia Broadcasting System, Inc., provide a new facility for research in communications. The Laboratories consist of three departments: Acoustics and Magnetics, Vacuum Tube and Solid State Physics, and Electronics Systems. The facilities of the Department on Acoustics and Magnetics comprise a wedge-type Anechoic Chamber, a laboratory for Transducer Research, a laboratory for Recording Research, a psychoacoustic testing facility, facilities for research on magnetic recording, magnetic fields and transducers, fine magnetic particles, and instrumentation.
Preliminary Investigation of Certain Aspects of Intonation
Authors: Denes P.
Published: September 2005

Intonation is the linguistic form in which the speaker organizes certain kinds of information. It is well known that intonation is related to the fundamental frequency pattern of the speech wave, but it must also be related to changes along other acoustic dimensions because the intonation “tones” are still recognizable in whispered speech. The fundamental frequency, intensity, spectrum, and duration changes associated with six intonation “tones” were investigated. The need for further work of this kind was indicated. The relation of acoustic variables and intonation was further investigated by using speech synthesis. Syllables with the same spectrum and intensity were generated in which the fundamental frequencies were controlled by the intensity variations of humanly produced syllables spoken on six different intonation “tones.” The test established that the synthesized syllables conveyed some of the information about the intonation of the humanly produced syllables. Methods for carrying out experiments on intonation with phonetically untrained subjects were investigated. The need for further experiments using methods of speech analysis and synthesis along lines indicated is pointed out. The importance for analysis-synthesis telephony of more extensive knowledge about intonation is discussed in some detail.
Measurement of Digital Channel Capacity for a Speech Compression System
Authors: Bach R. E. , Howard C. R. , Chang S. H.
Published: September 2005

It has long been speculated that an information handling rate of 1000 binits/sec or lower might be adequate for transmission of speech, if first the redundancy of its original form could be reduced. The Formoder, a speech-band-compression system, accomplishes the reduction by extracting the main information-bearing elements from speech, presenting them in a seven channel output which requires a total band width of about 175 cps. Latest articulation tests using Harvard P.B. word lists processed by the Formoder and given to a trained crew have yielded scores of 75% and higher for some male speakers. In order to measure the digital channel capacity necessary to intelligibly transmit the Formoder output, the seven channels were digitized using a technique known as “delta modulation.” This scheme achieves time and amplitude quantization by means of a clipper, sampler, and a linear feedback network. Compared with standard pcm techniques, “delta modulation” represents considerable economy in instrumentation. Articulation tests were made for several rates in the range 500–2500 binits/sec. Results of these tests will be reported and the important features of the digitizing technique will be given. [This research is sponsored by the Air Force Cambridge Research Center under Contract No. AF 19(604)-3465.]
Message Reception and Message Repetition
Authors: Pollack Irwin
Published: September 2005

The improvement in word intelligibility associated with successive presentations of a word in noise was examined with recorded or independent samples of the speech and/or its background noise. The listener's criterion for termination of a trial was shown to be a crucial determinant of the gain of intelligibility with successive presentations. The improvement in intelligibility was greater for independent samples of speech and noise than for successive presentations of a single recorded sample. The observed improvement, however, was less than predicted for the ideal observer with perfect memory by the theory of signal detectability. Indexes of response discriminability and signal discriminability are briefly discussed.
Magnetostrictive Properties of Certain Cobalt-Nickel Alloys
Authors: Harris W. T. , Farr H. K. , Clark C. A. , Wise E. M.
Published: September 2005

The magnetostrictive, magnetic, and elastic properties of pure nickel and certain cobalt-nickel alloys have been examined. Tests in two laboratories utilizing different equipment, including a new type of vector impedence bridge, showed that an electromechanical coupling coefficient of 0.5 could be secured with the 412% cobalt-nickel alloy—over 50% higher than that of pure nickel. Ring-shaped resonators were prepared, supported in low loss mounts, which exhibited Q's of the order of 300. This new alloy is particularly useful in increasing the efficiency of broad-band magnetostriction transducers.
Pitch Recognition for Isolated Musical Tones (Absolute Pitch)
Authors: Ward W. Dixon
Published: September 2005

The ability of certain individuals to identify, more or less accurately, isolated musical tones has been a subject of speculation for many years. The present paper will review the opinions of the more noted speculators and the meager empirical evidence (experimental and observational) on which explanations of absolute pitch are based, Differences and similarities between absolute pitch and analogous abilities in other sensory modalities will be discussed, especially in regard to information-handling capabilities of the various sensory systems.
Detection with Underwater Sound; Comments on the Present State of the Art
Authors: Rudnick Philip
Published: September 2005

Defense is offered for use of likelihood ratio considerations in designing a computer for detection. apart from doctrine for the detailed use of the computer output. There is needed: (a) full experimental investigation of the performance of Gaussian likelihood ratio computers, for which usable design theory is available, (b) theoretical effort toward using achievable empirical input statistics in approximating the likelihood ratio, (c) theoretical interrogation of the likelihood ratio principle for means of dealing with specific and strategic kinds of non-Gaussian behavior in the input noise, and (d) empirical examination of actual background noise for the same kinds of non-Gaussian behavior. (This work represents results of research carried out under contract with the Office of Naval Research.)
Theoretical and Experimental Study of Underwater Sound Reverberation
Authors: Cron B. F. , Schumacher W. R.
Published: September 2005

A theoretical study of the fluctuation of the amplitude and phase associated with the return of a single frequency pulse was made. A vectorial representation was used. From this model, the conditions necessary for a first-order Rayleigh distribution of amplitudes are given, and the second-order probability distribution of the amplitudes is derived. Experimental tests were conducted in the Bermuda area. Data on volume reverberation, as well as surface return and surface plus bottom return, were obtained. The data were processed via the USL Datrac-Datatron system. Analog as well as digital processing was used. An analog electronic circuit was used to generate the Hilbert transform of the returned signal. The return signal and the Hilbert transform were both sampled by the “Datrac” system at a rate of the reciprocal of the bandwidth. The analog values thus obtained were then converted to digital form by the “Datrac” system. From the digital values of the original time function and the Hilbert transform of the time function, the Datatron 205 was programmed to compute the corresponding values of the envelope and the phase of the carrier frequency. Experimental histograms were obtained by the computer for these values. The experimental histograms were compared with the expected theoretical distributions. Statistical tests of goodness of fit were conducted on these data. The results showed the theoretical assumptions to be valid.
Acoustic Modeling in Architecture
Authors: Christoff Jerry P. , Veneklasen Paul S.
Published: September 2005

Effective calibration and equalization of the Western Electric 640AA microphone to 100 kc advances the prospect of effective small-scale model studies in architectural acoustics. A small air jet source having appropriate noise spectrum in the range of 14 to 70 kc is used with models as small as 14 in. per ft. The acoustic model technique is effective in conjunction with optical modeling as developed by R. W. Leonard. A preliminary view of the utility of the technique is illustrated with data on absorption of direct sound over a sloping audience surface and the development of improved balcony soffit shaping.
Application of Low-Frequency Absorbers to Auditorium Acoustics
Authors: Sepmeyer L. W. , Leonard R. W.
Published: September 2005

The absorption characteristic of a seated audience and the enclosed air in an auditorium are such as to require predominately low-frequency absorption on the side walls in order to achieve a desirable reverberation characteristic. This paper will discuss the design and performance obtained in the Long Beach City College Auditorium by using the fireproof resonant absorbers previously described by the authors [J. Acoust. Soc. Am. 26, 937 (1954)] on the side walls together with oil-drum resonators in the ceiling. The resulting reverberation characteristic ranges from about 2 sec to 40 cps to 1 sec at 8 kcps.
Measurements of Ultrasonic Absorption and Velocity in Silicones
Authors: Carome Edward F. , Hunter J. L. , Pasquesi R. J.
Published: September 2005

Measurements of the ultrasonic absorption and velocity in Dow Corning 200 Fluids of various viscosity grades were made at a temperature of 20°C for different frequencies from 10 to 90 Mc, using a pulse technique employing transmitting and receiving crystals. Relaxation is indicated both by falling α/ν2 curves and values of α/ν2 which are very small compared to the Stokes low-frequency value. As an indication, the theoretical low-frequency value for 1000 Stokes Silicone Fluid is 26 000 × 10−15 cm−1 sec2, where the present measurements give 15.5 × 10−16 cm−1 sec2 at 10 Mc, falling to 6.6 × 10−15 cm−1 sec2 at 90 Mc. The curves give no accurate indication of the relaxation frequencies, other than that they are apparently much lower than the region of measurement. No dispersion was detected. (This work was supported in part by the office of Naval Research.)
Dispersion Measurements in Carbon Disulfide
Authors: Carome Edward F.
Published: September 2005

Measurements of the dispersion of the velocity of ultrasound in carbon disulfide have been made. The ranges of temperature and frequency under investigation span large portions of the relaxation regions made evident by previous absorption studies. A description of the experimental techniques employed to obtain accurate velocities at the higher frequencies will be presented. The results of the measurements will be compared with the predictions of both single and double relaxation theories. (This work was supported in part by the office of Naval Research.)
Ultrasonic Absorption in Fused Chlorides
Authors: Marchessault J. G. , Litovitz T. A.
Published: September 2005

Ultrasonic absorption and velocity were measured in the molten state of the chlorides of lithium, sodium, potassium, cesium, and silver. Measurements were made at frequencies between 100 and 145 Mc over a temperature range from 450°C to 900°C. The observed attenuation was found to exceed the classical value by a factor of about 20. The mechanism of attenuation is assumed to be a structural relaxation effect as in water and the molten nitrates. The temperature dependence of the bulk viscosity, although negative, was found to differ from that of the shear viscosity. Differences in activation energies of as high as 6 kcal per mole were noted. As is the case for the nitrates and the primary alcohols, the ratio of bulk to shear viscosity was found to be an exponential function of the entropy of fusion. In addition it was found that this ratio was a linear function of the volume change upon fusion. (Supported by the Office of Ordnance Research.)
Temperature and Pressure Coefficients of Sound Velocity in Ethyl Alcohol
Authors: Wilson Wayne
Published: September 2005

The velocity of sound in ethyl alcohol was measured in the temperature range 0.3⩽T⩽58.0°C for pressures between 1.03 kg/cm2 and 1000 kg/cm2. An empirical equation was fitted to the velocity data in these ranges and differentiated to give tables for (∂C/∂p)T/C and (∂C/∂T)p/C. The ratio of the temperature coefficient of density to the temperature coefficient of sound velocity was computed to show that Rao's constant is a function of temperature and pressure. The ratio 1ρ(∂ρ∂P)T⧸1C(∂C∂P)T = −21 − (∂B/∂P)T, (1) where B is the isothermal bulk modulus, is independent of temperature and varies nearly linearly with pressure. Kittel's equation for the available volume model of liquids and the equation for the free volume model (Eyring and Hirschfelder) were differentiated and substituted in Eq. (1). The results will be compared with the information obtained from the present work.
Sonic Fatigue of a Simple Notched Panel
Authors: Dyer I. , Smith P. W. , Gogos C. M. , Malme C. I.
Published: September 2005

Fatigue measurements on a panel designed for basic sonic fatigue studies are described. The panel is a 12-in. thick, 2024 T3 aluminum bar, 2 in. wide and 25 in. long. At each end of the bar, groove-like notches are machined to provide thin webs. The strain concentration in the web is 6 for the fundamental flexural mode of the bar. The thin web also provides a hinged boundary condition for the bar and thus simple sinusoidally shaped bar modes. To eliminate the complication of nonlinear motion of the bar. the boundary clamps are relieved in the neutral plane. The bar is mounted in the side of a duct and is excited into flexural motion at resonance by a sound wave in the duct. A novel method of fatigue detection by measurement of clamp reaction is described. Fatigue measurements with pure tones show good agreement with other test methods. It is hoped that the results of fatigue measurements with complex wave forms and multimodal excitation also will be available for presentation. (Supported by Wright Air Development Division.)
Vibration Studies of Plates
Authors: Skudrzyk E. J.
Published: September 2005

The solution for a circular plate excited to transverse vibrations by a periodic point force at its center is derived in closed form. The result is used to develop the theory of sound propagation in plates, similar to the theory of reverberation in room acoustics. In the computations the plate is represented by its sound velocity for bending waves and its characteristic impedance.
Plate Damping by a Constrained Viscoelastic Layer: Partial Coverage and Boundary Effects
Authors: Kerwin E. M. , McQuillin R. J.
Published: September 2005

An analytical investigation of the effects of boundaries on the damping of plates by constrained viscoelastic layers has been carried out as an extension of earlier work [E. M. Kerwin, Jr., J. Acoust. Soc. Am. 31, 952 (1959)]. It is assumed that the plate is in vibration with straight-crested one-dimensional flexural waves. Various geometries of plate and constraining layer are considered: infinite, semi-infinite, and finite plates; and semi-infinite and finite constraining layers. Boundary conditions considered are: supported, free, and clamped for the plate, and free and clamped for the constraining layer. By calculating the energy dissipation near the boundary relative to what it would be far from the boundary, a measure of the damping efficiency near the boundary may be obtained. Such energy ratios are presented for the various cases. It is found that the local dissipation near the boundary can be either greater or less than the “far-field” dissipation. These edge effects occur principally within the first half wavelength from the boundary. Numerical calculations were carried out on a high-speed digital computer. [This work was supported by the U. S. Air Force, Wright Air Development Center (subcontract from the University of Minnesota), and by the U. S. Navy, Bureau of Ships.]
Sonar, the Submarine and the Arctic Ocean
Authors: Lyon Waldo K.
Published: September 2005

During the past 14 years, the development of special sonars has made the exploration of the entire Arctic Ocean possible by submarine during either winter or summer. Sonar is required to detect ice that extends down to cruising depth. Information regarding the distribution and thickness of the ice canopy is required in order to choose an area in which the submarine can surface. Sonar must then guide the surfacing through the ice sheet. What little information is available on acoustic properties of sea ice indicates that, in the 15- to 50-kc region, sea ice acts primarily as a volume scatterer of sound in contrast to a diffuse reflector. Upward refraction is the dominant, stable sound transmission condition in the Arctic Ocean and enhances the importance of the acoustic properties of sea ice in determining long-range sound transmission. The acoustic properties of sea ice probably change greatly with temperature and history of growth.
Recent Sound-Speed Measurements Utilizing the Bathyscaph “TRIESTE.”
Authors: Mackenzie K. V.
Published: September 2005

Two Bureau of Standards velocimeters and Nansen bottles were mounted on the bathyscaph to obtain “in situ” measurements. Data were obtained by A. B. Rechnitzer for the author at depths of 2000 and 5600 m as well as in the 29°C surface waters. Subsequently the velocimeters were taken to the Arctic and lowered from a surface vessel. Nansen bottles with reversing thermometers were tripped to match velocimeter measurements both on the bathyscaph and in the Arctic. The relationships obtained between the sound speeds, temperatures, salinities, and depths will be discussed and compared with measurements by Wilson and Del Grosso.
Prediction of Aircraft Interior Noise Levels
Authors: Large John B.
Published: September 2005

The current techniques available for predicting interior noise levels are outlined, and the limitations of these techniques, particularly in their application to future high-speed aircraft, are discussed. The relative importance of each external noise source is discussed, with special emphasis on the boundary layer, the engines, and the wake. Interaction of the noise sources and the effect of this interaction on interior noise predictions are mentioned—for example, the interaction of the engine noise on the boundary layer pressure field. Also, the anticipated exterior noise levels for future aircraft are estimated. Presented curves, obtained from flight test data, laboratory measurements, and analysis, compare transmission loss through the fuselage side wall (skin plus soundproofing) of a modern transport airplane. In the commentary on these results, an attempt is made to explain the discrepancies between the predictions. The relative merit of each prediction method is discussed, together with that of another method, namely, a boundary layer test facility. In conclusion, the paper contains a brief discussion explaining the influence that aircraft interior noise requirements have on the design of fuselage side walls, including skin gage, damping properties, and stringer and frame spacings.
General Acoustical Design Considerations for Jet Aircraft Air Conditioning Systems Ground Support Equipment
Authors: Lepor M.
Published: September 2005

To achieve the acoustic goals in today's jet aircraft with attending ground support equipment requires a concentrated effort in the preliminary design stage. This effort is predicated in part on the extent of existing knowledge as to the effects of the various noise generating parameters. Where these are lacking, it becomes necessary to set up programs to evaluate complete systems, as in air conditioning, or structures as in ground cart cabinet design. This predesign effort with its attending programs becomes the more important because of the tendency today continually to lower the noise level environment in which the human inhabitant will be placed either as a passenger or as one of the ground maintenance crew. Because of the direction toward lighter structures, greater weight saving, greater outputs, and space and size limitations, every facet of acoustical design must be considered. An effort will be made to consider many of these facets and their accompanying noise evaluation programs.
Near and Far Fields of Multipoles and Jet Noise
Authors: Grimsal E. G.
Published: September 2005

The concept of quadrupoles, introduced by Lighthill in his theory of aerodynamically generated noise, was a new one to many investigators in acoustics and aerodynamics. Thus in some cases the nature of the quadrupole field and its origin have been misunderstood or misrepresented mathematically. In addition it is often forgotten that Lighthill's integral expression for the density fluctuation is an integral equation, because the unknown density is contained in the integral; when the average value of the density in the jet is used inside the integral, one obtains only a first approximation to the exact result. This latter point may not be important in the study of far-field noise from turbulence in a jet at low Mach numbers, but if the Mach number is high or if it is the near field that is to be studied these considerations become important. For example, in jets with velocity near Mach-one, the interaction between the jet structure and the near field of the quadrupoles cannot be neglected. This contributes another to the many correction terms of the order of M2 (which are compared for possibilities of mutual cancellation.) The complications arising in the quadrupole description of noise from jets with velocity near Mach-one make attractive any possible model using monopole or dipole sources. (This research was supported by the U. S. Air Force, Wright Air Development Division.)
Human Reaction to Jet Engine Noises
Authors: Little John W.
Published: September 2005

The subjective response of humans to jet noises was studied to determine the relative difference in subjective annoyance levels produced by different jet engine configurations. The noises studied were representative of jet airplane ground and fly-over operations. Further testing was carried out to determine the relative annoyance properties of random noise spectra which were characterized by the presence of outstanding single frequency tones. Emphasis was placed on discovery of the relationships between “spike” frequency, “spike” amplitude, and over-all sound pressure level. The results of this program are presented with comments on their use as a basis for more extensive programs of this nature.
Time Registration of Spoken Words Using a Reliable Voicing Measurement
Authors: Dersch W. C.
Published: September 2005

The detection of the beginnings of spoken words (necessary for machine recognition) has proved a difficult problem. Inaccurate identification produces shifting of subsequent word measurements on the time base axis, forcing additional complexity in decision logic. A solution to this problem is described in which a registration point is generated from an unambiguous event in the spoken word—not necessarily coinciding with the beginning of the word. From this registration point, provided by a simple and reliable voicing measurement, the actual word beginning (for the purpose of machine recognition) is then determined by extrapolation. The application of this technique to monosyllabic and polysyllabic words will be described, and experimental data will be presented.
Automatic Recognition of Spoken Numerals
Authors: Sebestyen George
Published: September 2005

A spoken numeral is represented by a vector in a 361 dimensional space constructed through use of an 18-channel Vocoder. In the quantized time-frequency plane representation of speech events each dimension expresses the amount of energy the spoken utterance contains in a given band of frequencies during a given interval of time. Utterances are reduced to a fixed duration, and the time normalization factor is included as one of the dimensions of the space. Linear transformations of the space (one for each of the class of digits zero through nine) are found by a computer so that, after transformation, a given set of vectors (points) which represent different utterances of the same digit become maximally clustered in the new space. Membership in the ten classes of spoken numerals is measured by ten different non-Euclidean metrics obtained from the Euclidean metric via the linear transformations. Thus different error criteria, each generated by members of a class of numerals, are used to measure the membership of an utterance in the ten classes of numerals. This technique was tried on 400 samples of the ten numerals spoken by ten speakers. Results of the experiment indicate that no errors in recognition were made when seven or more samples were used to compute the optimum linear transformations. This result was obtained when the numerals tested were spoken by persons other than those whose samples were given originally.
Digital Automatic Word Recognition Procedure
Authors: Petrick S. R. , Willett H. M.
Published: September 2005

An eighteen-channel Vocoder has been utilized in conjunction with the AFCRC magnetic computer in a real time word recognition study. This paper briefly describes this equipment and the manner in which it is used in both learning and recognition modes. Any new input word may be added to a computer vocabulary after several utterances and subsequent labeling of that word through the computer typewriter. In the recognition mode, previously learned words are identified and typed. Recognition of an unknown word is accomplished by selection from the computer vocabulary of the word closest to the unknown word as indicated by several measures. Formulas are derived for computing the optimal representation of a given word for the computer vocabulary from a number of utterances of that word. By using the previously described equipment and pattern recognition procedure, results have been obtained in several areas: (1) Over 2000 recognitions of digits between zero and ten involving thirty talkers have been made. Numerical and graphical recognition statistics on the number of correct selections and the margins by which they were picked are presented. (2) Speaker identification as well as numeral recognition has been studied using once again decimal digits for the restricted vocabulary. (3) The success of the method on several other restricted vocabularies has been investigated including German numerals and phonetically similar sets of words. (4) Careful study has been made of the sensitivity of the procedure to the sampling rate, number of frequency channels, and number of bits per channel of the Vocoder. The results show the effectiveness of the method of this paper as a function of those parameters.
Automatic Measurement of the Formants of Vowels in Diverse Consonantal Environments
Authors: House A. S. , Stevens K. N. , Fujisaki H.
Published: September 2005

The principle of analysis-by-synthesis, described in earlier papers, is applied to the measurement of the formant frequencies of the common vowels of American English. The vowels measured constitute segments of bisyllabic nonsense utterances recorded by three adult male talkers. The set of materials is designed to provide samples of stressed vowels preceded and followed by a variety of consonants. The vowels in question occur in consonant-vowel-consonant syllables in which both consonants represent the same phoneme of American English. Frequencies of the first three formants are measured throughout the vowel for spectral samples separated by approximately 8 msec. Effects on formant frequencies attributable to temporal location of sample, consonant environment, and individual talkers are discussed. For central locations of the samples, the formant frequencies differ systematically from published data derived from more restricted consonantal environments. Phenomena relating to formant transitions and individual talker characteristics are discussed. [This work was supported in part by the U. S. Army (Signal Corps), the U. S. Air Force (Office of Scientific Research, Air Research and Development Command), and the U. S. Navy (Office of Naval Research); and in part by the Air Force Cambridge Research Center.]
Spectrum Matching of Fricative Consonants
Authors: Heinz J. M.
Published: September 2005

The frequency spectra of the voiceless fricative consonants of American English have been studied using digital computer methods. The speech materials and computer program are described in papers on vowel formants and nasal consonants presented at this meeting. Spectra characterized by transfer functions having two or more pairs of conjugate poles and one or more pair of conjugate zeros, together with simple source spectra, are generated in the computer for comparison with speech spectra in the steady-state portions of the fricatives. Also shown are examples in which the formants of the adjacent vowels are traced continuously through the transitions and into the consonants. Data on the position of the poles and zeros required to obtain a good match are given. The results will be related to an acoustic theory of fricative production. [This work was supported in part by the U. S. Army (Signal Corps), the U. S. Air Force (Office of Scientific Research, Air Research and Development Command), and the U. S. Navy (Office of Naval Research); and in part by the Air Force Cambridge Research Center.]
Some Allophones of /r/ in American English
Authors: Lehiste Ilse
Published: September 2005

The study reported in this paper deals with the acoustic characteristics of initial, final, medial, and syllabic allophones of /r/ in Midwestern American English. The description is based on a spectrographic analysis of 136 frame sentences, spoken by five informants. Some of the reciprocal influences between the positional variants of the /r/ phoneme and the preceding and following sounds are described. The possibility of identifying the syllable nucleus [ɝ] with one of the phonetic variants of /r/ is considered. It appears that certain of the allophones of /r/ have relatively stable formant patterns and that it is possible to associate those allophones with the boundaries of larger phonological units.
Consonantal Cues for Automatic Speech Recognition
Authors: Larkin Wilbur D.
Published: September 2005

A report is made on the investigation of 18 consonants (voiced and voiceless stops, affiricates, nasals /m/ and /n/, and fricatives /f, v, ð, θ, s, z, ȝ and ∫/) in combination with nine vowel phonemes /i, ɪ, ɛ, æ, a, ɔ, ᴜ, ʌ, and u/. This study is based upon both the transitions of the first four formants and the spectral distribution of energy of the stop and fricative bursts. The data for the investigation were obtained from subjects recording both consonant-vowel-consonant nonsense syllables and test words in sentences. The sentences were so constructed as to be identical except for the opposition of the consonant being investigated. The applicability of these data to consonants in middle and final position also is discussed. The results of this study and their application to an automatic speech recognition device are presented.
Some Aspects of Acoustical and Cineradiographic Analysis of Newborn-Infant and Adult Phonation and Associated Vocal Tract Activity
Authors: Truby H. M.
Published: September 2005

A 16-mm cineradiographic sound film will be shown demonstrating certain critical vocal tract articulatory activity during speech. Particulars of this film will be discussed in correlation with sound spectrographic and over-all intensity analysis, as adjunctive, at the acoustic signal level, to general machine translation considerations. Apparent successivities such as the sounds corresponding to the “pl-” or “plea,” e.g., are shown to have simultaneous presentation of positive sound criteria. Affricates are physically analyzed as “simultaneities,” while “clusters,” by the same principles, must be classified as “successivities.” A technique for making microchronomatic (down to 4000 parts of a second) investigation of acoustic signals utilizing tape-segmentation-along-the-time-axis is presented in some detail, both in reference to the presentation and perceptual evaluation of speech sounds and of sounds generated in the infant vocal tract during natal transition. Mechanical segmentation (such as tape segmentation) demands special consideration in perceptual analysis, especially as regards its contrast with linguistic segmentation; reference is made to pertinent evaluation criteria. Some statements regarding the application of natal transition vocal tract sound analysis to clinical diagnosis and its potential value as part of the newborn's permanent record are offered for discussion.
High-Frequency Ultrasonic Sound Probe for Making Near-Field Acoustic Measurements
Authors: Thompson John H.
Published: September 2005

This paper briefly describes the construction and test results of an ultrasonic sound probe used for measuring the particle velocity at the face of elements in a hydrophone array. The problems of Fresnel zone interference and field disturbances make near-field measurements of pressure difficult to interpret. The sound probe described overcomes these difficulties by measuring the particle velocity. This is accomplished by proper mechanical and electrical loading. Comparison of the results is shown by use of velocity probes and pressure probes.
Ceramic Cylinders for Lower Frequencies, Lower Impedances, and Greater Depths
Authors: Green Charles E.
Published: September 2005

The diameter of cylindrical transducers employing the radial mode of operation can be extended to permit resonant operation to much lower frequency. Heretofore the techniques for assembly of bars into cylinders have limited the practical physical size because of the dimensions of available ceramic bars. This paper describes an assembly method whereby available barium titanate bars can be oriented to provide cylinder wall thicknesses up to 12 in. A 200-in. diameter transducer will have an operational depth of 10 000 ft without pressure compensation and will resonate at 160 cycles per sec. This cylinder can supply 2 megawatts of acoustic power, essentially nondirectional. The same construction technique can be employed on units for frequencies up to 2000 cycles per sec. The paper also will indicate the power capability as a function of size, and stacking procedures are shown to realize the optimum source levels. Cylindrical transducers of nickel ferrite employing the conventional technique with permanent magnets installed have measured efficiencies of 69%. Properly associated windings permit a very low electrical impedance. Comparable transducers employing the barrel stave and the brick wall techniques have been evaluated.
Use of a Diverging Reflector to Increase the Beam Width from a Projecting Transducer
Authors: es Reuben H.
Published: September 2005

Requirements of wide beam width and high source level at high frequencies are often incompatible for flat-faced projectors. A solution to this problem has been to construct the transducer of many elements with these elements mounted on an arc whose length and radius of curvature are chosen for the proper beam width. Transducers of this configuration are difficult and expensive to build. This paper will describe a transducer which uses a relatively large aperture source and a diverging reflector to achieve the desired beam width. (This work was supported by contract with the Bureau of Ships.)
Triplane and Corner Reflector Targets for Underwater Sound
Authors: Hillery Herbert V.
Published: September 2005

Although the use of triplanes as artificial sonar and radar targets is well known, little consideration apparently has been given to the effect which particular configuration and structure has upon triplane target strength. This paper describes an experimental study of the characteristics of triplanes and corner reflectors constructed in varied shapes from various materials. In particular, methods of constructing triplanes having varied relationships between target strength and frequency are described. An argument is advanced that suitably constructed corner reflector targets can constitute excellent standards of target strength. (This work was supported by contract with the Office of Naval Research.)
Sound Radiation and Radiation Loading of Spheroidal Surfaces
Authors: Junger Miguel C.
Published: September 2005

The theory of sound radiation by spheroids has been used by the author's firm to obtain approximate solutions to a number of practical problems involving finite cylindrical and nearly spheroidal surfaces. The near-field solutions have beeen applied to the evaluation of radiation loading of ship hulls vibrating in various modes and to cylindrical underwater transducers. The far field of spheroidal radiators has been used to study problems not adequately approximated by the Laird and Cohen theory of sound radiation by infinite cylinders, viz., sound radiation by motions along the cylindrical axis and by transverse motions at frequencies when the length of the radiator is small in terms of wavelengths. (This work has been supported by the Office of Naval Research.)
A System for Automatically Recording Third and Higher Order Intermodulation Distortion Components
Authors: Burnett Edwin D.
Published: September 2005

A problem arises in measuring certain intermodulation distortion components when measurements are made at more than one set of input frequencies. When two input frequencies with a constant frequency difference between them are swept through the frequency range of interest, only some intermodulation components remain fixed in frequency. Others. which may be of significance, particularly in push-pull systems, change in frequency as the input frequencies are varied. A system is described in which some of these variable frequencies may be tracked by a slightly detuned reference frequency, which is derived by suitable heterodyning of the radio-frequency signals of two beat frequency audio oscillators. This signal serves as the reference signal in a non-phase-sensitive synchronous detector, the output of which is filtered, detected, and automatically recorded. (This work was done under the sponsorship of the Veterans Administration.)
Sound Reinforcement or P. A.?
Authors: Goodfriend Lewis S.
Published: September 2005

In many recent sound system installations, the results have been so poor as to make the rooms where they are installed unusable. In redesigning the sound systems we have applied the concept of sound reinforcement rather than the usual philosophy of the P. A. salesman. In many cases in school, church, conference room, and theater sound systems, excellent amplifiers are used in conjunction with high quality but suitable microphones and loudspeakers. In some cases basic errors in equipment location or the use of an unnecessary low-level system have caused system failure. Case histories illustrate the failure of a number of sound systems to meet the needs for sound reinforcement (dead spots, low intelligibility, intermittent ringing, mechanical or tinny quality) and the simple solutions to provide complete satisfaction for the owner.