bluuebunny/crossref_metadata_2025 huggingface dataset:
Speech Analysis-Synthesis Scheme Using Continuous Parameters
Authors: Howard Calvin G.
Published: September 2005

A device for processing speech for transmission over a narrow-band communication channel is described. This device analyzes the speech wave form and extracts certain parameters continuously as a function of time. These parameters have been used to control a speech synthesizer utilizing local excitation functions to simulate vocal and turbulent sources. Equipment to carry out the analysis-synthesis procedure as it exists in its present state is discussed as well as consideration for its inclusion in a complete band-width-compression system.
Electroacoustic Coupling at the Boundary of an Ionized Medium
Authors: Kornhauser E. T.
Published: September 2005

It is noted that an electromagnetic wave incident upon the boundary of an ionized medium in the presence of a transverse magnetic field will excite, in addition to the reflected and transmitted electromagnetic waves, a reflected sound wave and a transmitted modified sound wave. It is shown that the power coupled into these acoustic waves is proportional to the magnetohydrodynamic coupling parameter β = σ B2/ωρ and to the ratio of sound velocity to light velocity. Finally it is pointed out that electromagnetic transmission through a thin ionized layer may take place by means of this modified sound wave even though the layer thickness is large compared to the electromagnetic skin depth, although the efficiency of transmission will be very low for weak magnetohydrodynamic coupling.
Development and Testing of a Formant-Coding Speech Compression System
Authors: Flanagan James L. , House Arthur S.
Published: September 2005

The development of a speech-band-width compression system employing formant-coding principles is described. The compression system codes the input speech in terms of seven electrical signals, representing the frequencies of the first three formants, the amplitudes of voicing and of friction, the fundamental vocal frequency, and the frequency of the spectral maximum of the fricative excitation. These signals occupy a total band width of the order of 60 cps and require signal-to-noise ratios of approximately 30 db for their transmission.

An evaluation of the intelligibility of speech transmitted by the compression system is described. Natural monosyllabic utterances are transmitted through the system and presented to listeners for identification. Vowel and consonant articulation scores are computed and sound confusion matrices are constructed and discussed. The results indicate that correct identification occurred for approximately 80% of the vowels and 25% of the consonants.
Linguistic Prerequisites for a Speech Writer
Authors: Chao Yuen Ren
Published: September 2005

The first step in the construction of a speech writer must be concerned with the conversion of the flow of speech into discrete operations. Such operations have been brought within the realm of possibility by recent developments in the analysis and synthesis of speech in terms of frequency functions instead of pressure functions. The present paper deals primarily with the phonetic and graphic aspects of the response and discrimination required of the machine and the dictating person. Certain simplifications of design can be effected by consideration of the orthography of the language to be speech-written.
Theory of Stochastic Linear Systems with Gaussian Parameter Variations
Authors: Samuels J. Clifton
Published: September 2005

A theory of linear systems with randomly varying parameters is developed under the assumption that the parameter processes are Gaussian processes obtained by linear filtering of white noise. By this device, the restriction to white-noise parameter processes of previous studies has been removed.

By a method related somewhat to a technique used in the theory of the multiple scattering of light, a system of linear integral equations for the determination of various second-order moments of the system output is derived. This system can be solved explicitly in some interesting cases.

A theory of stability in mean and in mean square is given for random systems. It was found that mean square stability depended only on the values of the auto- and cross-correlation functions of the parameter processes at the origin and not on the detailed structure of these functions.

The stability theory is applied to an RLC circuit with randomly varying capacitance. The possibility of stabalizing unstable deterministic systems with random noise is discussed.
Stability of Shot Signals Transmitted through the Deep Ocean
Authors: Sherry H. B. , Berman A.
Published: September 2005

Shots were fired at a fixed location and constant shallow depth at 12-hr intervals over a period of 15 hr. Shots fired in this way produced a highly repeatable signal. The signals were received at a fixed location 63 miles away on hydrophones at 3000- and 9100-ft depths. The signals exhibit about 40% correlation over a period of 12 hr and about 20% correlation over a period of 1 hr.
Directivity of a Linear Array in a Random Transmission Medium
Authors: Bourret R. C.
Published: September 2005

A simple derivation is given of the phase autocorrelation function of a monochromatic signal during transmission through a medium with random fluctuations of refractive index. The resulting phase coherence function is then applied to the theory of the linear array antenna to yield a formula for the degraded directivity pattern.

The analysis developed here was conceived primarily with reference to acoustic signals and sonar ranging systems, although it may be applied, mutatis mutandis, to a wider variety of acoustic and even electromagnetic problems. For concreteness, however, we shall employ a vocabulary appropriate to the case of sonar signals and antennas.

The problem to be considered is the following: Given a source of monochromatic radiation situated far enough from the receiving antenna to be considered a point source, what will be the response, as a function of bearing angle, of a linear array antenna to the signal if the transmission medium has small random irregularities of its refractive index?
On Aerodynamic Sound from Dilatation and Momentum Fluctuations
Authors: Powell Alan
Published: September 2005

Physical reasoning suggests that aerodynamic sound from free flows may be attributed to local fluid dilatation coupled with local fluid accelerations, the former acting like a simple source field and the latter like a dipole field which reduces to a quadrupole field. A supporting mathematical development is given; it discloses the formal need of an additional surface integral. The rather poor convergence of the integrals is discussed and comparison is made with theories which rest on the dilatational effect alone.
Vibration of Simply Supported Flat Plates Simultaneously Tapered in Planform and Thickness
Authors: Klein Bertram
Published: September 2005

Accurate solutions are given for the first three natural frequencies of symmetric flexural vibration of simply supported flat plates that are simultaneously tapered in planform and thickness. The results are presented graphically, and the range of the values defining the geometry of the plate is considered large enough to cover most practical cases.
Contextual Constraints and Disruptions in Reading with Delayed Auditory Feedback
Authors: Fillenbaum Samuel , Wiesen Raymond
Published: September 2005

A re-examination of some data previously obtained by C. R. Elliott indicates that the absolute disruptive effect of delayed auditory feedback (DAF) is greater the greater the contextual constraint in a passage, and the more rapidly the passage is read under normal control conditions. The easier the reading task, the greater is the impairment in performance under DAF.
Physical Acoustics and the Properties of Solids
Authors: Mason Warren P.
Published: September 2005

The techniques of physical acoustics have been applied in determining the elastic properties and internal friction of polycrystal and single crystal metals, glasses, nonmetallic crystals, high polymer materials, and ceramics. They have been used as tools in investigating such solid state phenomena as grain and domain boundary effects in metals and ferromagnetic and ferroelectric materials, in the diffusion of atoms, molecules and vacancies through a solid, in the motion of imperfections such as dislocations and have even detected an interaction between the lattice sound vibrations and free electrons in metals at low temperatures.

These effects are studied by techniques varying from the vibrations of torsional pendulums at frequencies below 1 cy to frequencies as high as 300 Mc by ultrasonic pulsing methods and have employed strain values from 10−8 to 10−2. Four examples of these techniques are discussed in the present paper. These include diffusions of nitrogen and carbon atoms in iron, the motion of domain walls in ferromagnetic nickel, the interaction of lattice vibrations with free electrons at low temperatures and the use of high strain values in studying internal friction and fatigue in metals. These examples were chosen because they result in definitely explained effects which are indicative of typical processes occurring in solids.
Internal Friction and Fatigue in Metals at Large Strain Amplitudes
Authors: Mason W. P.
Published: September 2005

A barium titanate transducer coupled to an exponential horn can produce large strains in metals. By using a final horn with a necked down section, it is possible to concentrate the strains in a small specimen. Measurements of the impressed voltage and a voltage from a pick up electrode on the titanate make it possible to calibrate the device so that the internal friction, change in elastic constant, and the strain in the sample are all determined.

The measured internal friction can be divided into three strain regions. From 10−6 to 10−5 the internal friction is approximately independent of the strain. For strains from 10−5 to from 2 × 10−4 to 2 × 10−3, depending on the material, the internal friction increases with strain in a reversible anelastic manner. Above this range the internal friction increases very rapidly and for strains twice as large as those for the initial rise, the metal fatigues in a very short time.

It appears that the anelastic range is caused by the reversible production of unstable Frank-Read loops. The shape of the internal friction curve allows one to evaluate the dislocation distribution with results in accord with etch pit methods. The final phase appears to be due to irreversible production of Frank-Read loops caused by dislocations cutting through other dislocations. This process produces jogs in the dislocations and vacancies in the metal. These vacancies accumulate to produce fatigue cracks in accord with a theory of Mott's. Temperature and time effects result from the lowering of the activation energy by the applied stress. At liquid nitrogen temperature, the fatigue stress increases until the activation energy for diffusion is nearly zero.
Long-Range Localization of Small Underwater Charge
Authors: Frosch R. A. , Klerer M. , Tyson L.
Published: September 2005

Acoustic arrivals at 12 receivers from a large number of charges dropped across the North Atlantic Ocean were examined with regard to audibility and location. The probability of hearing a charge at one or more receivers was high, and the probable accuracy of the location determinations was under 10 miles.
Forward and Backward Masking between Acoustic Clicks
Authors: Raab David H.
Published: September 2005

The masking of one click by another was studied as a function of the time interval between the pulses. Two-alternative forced-choice procedures were employed to measure thresholds before and after the masking click. Both forward and backward masking were found; the forward effect was more pronounced and longer lasting. Backward masking studied in this way extends beyond what can be explained by peripheral intensity-latency conversions.
Attenuation of Ultrasonic Waves of Finite Amplitude in Liquids
Authors: Narasimhan V. , Beyer R. T.
Published: September 2005

Measurements are reported for the effect of finite amplitude on the attenuation of the fundamental component of an ultrasonic wave in water and in aqueous solutions of acetic acid and manganous sulfate. A two crystal continuous wave method was employed. The results in water indicate that the rate of increase of α/ν2 with pressure becomes less with increasing frequency. This result is in contrast to earlier results of Towle and Lindsay. The rate of increase of α/ν2 with pressure was lowered in the aqueous solutions as the concentration was increased.
Small-Scale Acoustic Streaming in Liquids
Authors: Kolb Josef , Nyborg Wesley L.
Published: September 2005

By using special acoustical and optical arrangements, vortex motions are discovered in the vicinity of small vibrating sources in liquids. Of particular importance is the vigorous eddying that typically takes place near a vibrating gas bubble when it rests on a boundary. This bubble-associated streaming has been observed under a variety of circumstances, and apparently occurs quite generally. Especially violent and chaotic motions appear near bubbles of resonant size. The attendant highly localized convection and viscous stresses are probably very important as intermediate physical mechanisms for sonic irradiation effects.
Voice Level: Autophonic Scale, Perceived Loudness, and Effects of Sidetone
Authors: Lane H. L. , Catania A. C. , Stevens S. S.
Published: September 2005

The speaker's numerical estimation of his own vocal level, the autophonic response, was found to grow as the 1.1 power of the actual sound pressure produced. When listeners judged the loudness of another speaker's vocalization (the phoneme [a]), the exponent was 0.7. The disparity between these exponents suggests that the speaker does not rely solely upon his perception of loudness in judging his own relative vocal level. The minor role played by loudness in the autophonic judgment is further demonstrated by the fact that the form and exponent of the subjective scale for autophonic responses remain relatively invariant under wide changes in auditory feedback.

The power laws governing the autophonic response (exponent 1.1) and loudness (exponent 0.6) were used to predict successfully the outcome of cross-modality comparisons in which subjects tried to match their vocal level to sounds of various intensities presented either by loudspeaker or by earphone. The slope of the matching function, relating the criterion SPL to the vocal SPL in log-log coordinates, is given by the ratio of the two exponents.

Unless the speaker tries deliberately to hold a constant level, the amount of sidetone gain with which the voice is fed back to the ears alters the voice level. The degree to which the speaker lowers his voice when the sidetone is increased is also predicted by the exponents governing the autophonic scale and the loudness scale.
Pressure Response of Condenser Microphones at Low Ambient Pressures
Authors: Chalupnik James D. , Rule Eric , Suellentrop Fred J.
Published: September 2005

The frequency response characteristics of condenser microphones at low ambient pressures are of interest when such microphones are used to make measurements on high-altitude rockets and capsules. Pressure response curves at a number of ambient pressures in the range 106 d/cm2 (atmospheric pressure at sea level) to 1.7×104 d/cm2 (atmospheric pressure at 90 000 ft alt) have been obtained for two commonly used condenser microphones (Western Electric 640AA, Bruel and Kjaer type 4111). Features of the response curves are discussed from a qualitative point of view.
Note on Pitch-Synchronous Processing of Speech
Authors: David E. E. , McDonald H. S.
Published: September 2005

Voiced portions of speech waveforms are quasi-periodic in nature. This property arises from repeated excitation of the slowly changing vocal cavities by glottal puffs. Knowledge of this periodicity affords a means for reducing the channel capacity necessary to transmit a speech signal. One proposal to this end involves eliminating N − 1 of every N pitch periods before transmission, where N is chosen small enough so that variations important to the ear-cortex in the intraperiod wave form are preserved. Thus, provided consonants are similarly chopped, the channel capacity in bits/second can be reduced by 1/N. At the receiver, missing parts are restored by interpolating them in a predetermined way, for example, by simply repeating each of the received periods N − 1 times.

Circuits for operating on monotone speech demonstrating this principle have been constructed. Experiments with N = 2, 3, and 4 indicate that minor distortion, which appears as submultiples of the pitch harmonics, is thereby introduced. Consonants are little affected by the chopping.

A similar scheme which involves eliminating portions of the wave form in each period was also investigated. Less satisfactory results were obtained here, since the intraperiod wave form carries the phonemic information.
Ultrasonic Relaxation and Axial-Equatorial Isomerization in Methyl Cyclohexane
Authors: Piercy J. E.
Published: September 2005

The ultrasonic absorption and velocity of dilute solutions of methyl, chloro-, and bromocyclohexane in xylene have been measured over the range 0.6 to 25 Mc and 65° to 95°C. The frequency dependence of the absorption in all cases is that of a single relaxation process. The concentration dependence of the relaxation parameters is consistent with the mechanism being the interchange of axial and equatorial chair isomers, while the temperature dependence yields a difference in enthalpy and entropy between isomers of methyl cyclohexane of 3.54±0.7 kcal/mole and 4.04±1.1 cal/mole °C, respectively, and an activation energy for the conversion of axial into equatorial isomers of 10.94±0.8 kcal/mole for methyl cyclohexane and 12±2 kcal/mole for chloro- and bromo-cyclohexane. There is no significant change in these values for methyl cyclohexane when the solvent is changed to nitrobenzene or n-butyl alcohol, indicating that intermolecular processes do not make an appreciable contribution, and that the difference in volume between isomers can be neglected in the calculations. The conversion of axial into equatorial isomers is found to be uni-molecular, and a mode of vibration of the molecule similar to either the A1g or Eu modes of cyclohexane is suggested for the path of this reaction.
Theory of Rectified Diffusion of Mass into Gas Bubbles
Authors: Hsieh Din-Yu , Plesset Milton S.
Published: September 2005

The problem considered is the behavior of a gas bubble in a liquid saturated with dissolved gas when oscillating pressures are imposed on the system. This situation is encountered in experiments on cavitation and in the propagation of sonic and ultrasonic waves in liquids. Since gas diffuses into the bubble during the expansion half-cycle in which the pressure drops below its mean value, and diffuses out of the bubble during the compression half-cycle in which the pressure rises above its mean value, there is no net transfer of mass into or out of the bubble in first order. There is, however, in second order a net inflow of gas into the bubble which is called rectified diffusion. The equations which determine the system include the equation of state of the gas in the bubble, the equation of motion for the bubble boundary in the liquid, and the equation for the diffusion of dissolved gas in the liquid. In the solution presented here, the acoustic approximation is made; that is, the amplitude of the pressure oscillation is taken to be small. It is also assumed that the gas in the bubble remains isothermal throughout the oscillations; this assumption is valid provided the oscillation frequency is not too high. Under these conditions one finds for the mean rate of gas flow into the bubble the expression 〈dm/dt〉 = (8π/3)DC∞R0(ΔP/P0)2, where D is the diffusivity of the dissolved gas in the liquid, C∞ is the equilibrium dissolved gas concentration for the mean ambient pressure P0, R0 is the mean radius of the bubble, and ΔP is the amplitude of the acoustic pressure oscillations. It may be remarked that the most important contribution to the rectification effect comes from the convection contribution to the diffusion process.
Response of the Human Skull to Mechanical Vibrations
Authors: Franke Ernst K.
Published: September 2005

Measurements of the mechanical impedance and of the vibration pattern of the human skull are described. In the frequency range from 200 to 1600 cps the skull was excited to vibrations by means of an electrodynamically actuated piston with small contact area. Data were obtained from living subjects, a dry skull preparation, and a human cadaver. The modulus of elasticity of skull bone, calculated from the resonance frequency of the skull, was found consistent with the value obtained by static methods. The propagation velocity of flexural waves in the skull bones, as calculated from the natural frequencies, agrees satisfactorily with the experimentally determined velocity. It is shown, finally, that a vibrating spherical shell is a suitable model for the skull and describes its vibration patterns with good approximation.
Sound Waves in Deformed Perfectly Elastic Materials. Acoustoelastic Effect
Authors: Toupin R. A. , Bernstein B.
Published: September 2005

The general equations for a small displacement superimposed on a finite deformation of a perfectly elastic material of arbitrary symmetry are derived anew. These equations are the basis of an analysis of plane waves of small amplitude propagating in an initially deformed and stressed elastic material. Certain restrictions on the energy function of finite elasticity theory are determined. These restrictions, which provide necessary and sufficient conditions that a homogeneously deformed material admit plane waves, are then compared with other restrictions obtained from themostatic equilibrium considerations. Compatibility conditions, which are necessary and sufficient that data on sound wave propagation in elastic materials be compatible with classical elasticity theory upon suitable assignment of the material symmetry, are derived. Finally, it is shown how the variation of sound speeds with initial stress and the measured magnitude of the acoustoelastic effect can be used to determine the third-order elastic constants of an isotropic material and as a partial confirmation and experimental check of the theory.
Analog Circuit Representation for Wall Panels
Authors: Frost Albert D.
Published: September 2005

A new approximate equivalent analog circuit representation for wall panels is proposed. This circuit is in the form of an extended network of interconnected mesh structures. Solutions for the fractional energy transfer through the system are given for various source and boundary conditions. Experiments on a lightweight panel using a simulated plane-wave source give values of transmission loss which are comparable to those using coupled chamber techniques.
Signal Amplitude and Phase Fluctuations Induced by Surface Waves in Ducted Sound Propagation
Authors: Scrimger Joseph A.
Published: September 2005

The effects of surface waves on sound propagated from a continuous wave source over a range of 300 it in water of depth 10 ft have been examined. It is found that the surface waves induce regular amplitude and phase fluctuations in the received signal. The dependence of the amount of amplitude and phase fluctuation on crest to trough height of the surface waves has been obtained for acoustic frequencies in the range 1 to 10 kc. Frequency spectra of the fluctuations, for values of the ratio of sound wavelength (λ) to wave height (A) above 18, are the same as the surface wave spectra. For values of λ/A less than 18 the fluctuation spectra are broader and show well defined second and sometimes third harmonic components. Wave packet experiments in which the bow wave of a small boat is propagated across the length of the otherwise calm duct surface show that in the case of the uniformly rough surface the fluctuations are produced only by surface waves near the source and near the receiver.
Realization of Prosodic Features in Whispered Speech
Authors: Meyer-Eppler W.
Published: September 2005

Experiments utilizing a visible-speech analyzer showed that changes of pitch in normal (voiced) speech are replaced in whispered speech by shifts of some formant regions accompanied by added noise between the higher formants.
Some Results of Research on Speech Perception
Authors: Liberman Alvin M.
Published: September 2005

Recent experiments with synthetic speech have succeeded in isolating some of the acoustic cues which underlie the perception of speech. This paper describes, and attempts to interpret, some of the research in that area.
Intelligibility of Time-Compressed Speech
Authors: Klumpp R. G. , Webster J. C.
Published: September 2005

By automatically reassembling periodic samples of recorded speech, Fairbanks and associates have shown that comprehension is good for: (1) connected speech compressed 50% (0.5) in time, and (2) a single well-learned PB list compressed up to 0.15. In 1919–1925 Fletcher and associates, using turntable speedup with its attendant frequency distortion, found that the intelligibility of syllables began to drop rapidly at speedups corresponding to time reductions of 0.8 (down about 25% at 0.7). In one case a complex technique using simple language showed only slight losses in comprehension for large time compressions. In the other case, a simple technique using difficult speech material showed marked deterioration. In our work on message (simple language) storage schemes, the desirability of obtaining time compressed speech with simple modifications of existing equipment has become evident. By merely speeding up the playback of a tape recorder, we have found that numbers and simple phrases can tolerate a time compression of 0.67 without serious losses in intelligibility, and PB words lose only 10%, in intelligibility with a time compression of 0.75.
Objective Allocation of Sound-Image from Binaural Stimulation
Authors: Kikuchi Yoshimitsu
Published: September 2005

This paper describes two methods for making an objective quantification of the location of the sound image that results from binaural acoustic stimulation. The first method (“nullity method”) is based on reversing, by means of a changeover device equivalent to a double-pole, double-throw switch, the binaural signals—switching the signal from the right ear to the left ear and the signal from the left ear to the right ear. Adjustments are made in one of the two channels until this reversal does not appear to change the location of the sound-image. The second method (“comparison-sensation method”) involves a pilot signal, which is applied binaurally and used to produce a reference image with which the experimental sound image is compared. These methods are more objective than the ones usually employed because they require the observer to function only as a null indicator. Data are presented which show that the “nullity method” yields data that are much less variable than those obtained with the ordinary method.
Concerning New Methods of the Measurement of Hearing in Man
Authors: Gersuni G. V.
Published: September 2005

It is known that the main quantitative characteristics of hearing in man can be obtained by so-called psychophysical methods. In these methods the responses to sound stimuli are based upon the use of verbal instructions.

This paper gives a description of methods of measurements of hearing based upon the use of other different responses to sound stimuli.

A set of different conditioned responses was used (galvanic-skin reflexes, eyelid reflexes, electrocortical and oculomotor reactions). The data obtained by these methods show the following: (1) absolute auditory thresholds and difference limens for frequency and intensity of pure tones can be measured with the same accuracy by these reactions as by verbal responses; (2) in certain cases conditioned reflexes subliminal to the verbal response in the range of 1 to 6 db may be detected; (3) changes of absolute sensitivity, attaining 25 to 30 db and dependent on the conditions under which the reactions take place, can be detected.

The present data of hearing measurements obtained by means of different responses are considered as highly characteristic of the process of sound discrimination in man and animals.
Absolute Judgments of Musical Tonality
Authors: Corso John F.
Published: September 2005

The purpose of the present study was to determine the accuracy with which college musicians could make absolute judgments of equally-tempered tonalities. The stimuli consisted of three randomly-ordered presentations of twelve major and twelve minor keys within each of three series of tape-recorded piano tones. Series I consisted of eight-tone ascending diatonic scales; Series II, the eight tones of the diatonic scales randomized for each key; and Series III, sequences of four chords. The results of the study indicate that judgments of the twenty-four specific keys axe most often correct for the ascending scales and least often correct for the randomized “scales.” The identification of major and minor modes is, on the average, not perfect, but is increased when the subjects are instructed to judge only modes, disregarding key-names. In general, major keys are more often correctly identified than minor keys. It is suggested that judgments of musical tonality are probably multi-dimensional and influenced by set.
Synthesis of Stepped Acoustic Transmission Systems
Authors: Holte J. E. , Lambert R. F.
Published: September 2005

Procedures are described whereby acoustical systems supporting one-dimensional harmonic waves may be synthesized for a prescribed frequency dependence of the input reflection coefficient. An important design latitude is gained by allowing the nominal characteristic impedance of the structure to vary in a stepwise manner with the independent space variable. An initial simplified model is presented which assumes only propagating plane waves and neglects multiple reflections between discontinuities. These results are corrected to include the effects of multiple reflections by techniques from signal flow graph theory. Effects of local higher-order modes existing at the discontinuities are represented as lumped shunt susceptive elements. Data obtained from measurements on an acoustic matching section design operating between a 5.76:1 impedance mismatch over a 50% bandwidth centered about 1333 cps confirm the theoretical predictions. Further data, obtained from standing-wave measurements at the input to coupled resonator sections, indicate the importance of higher-order nonpropagating modes when the discontinuities are large. It is found that effects of these modes upon the input reflection coefficient are readily obtained from Smith chart calculations.

The synthesis procedures constitute a simple, rapid means for initial design of a stepped structure to yield a prescribed frequency dependence of input reflection coefficient by essentially graphical techniques. The most important unsolved problems are the direct inclusion of multiple reflections and susceptive discontinuity effects in the synthesis procedure and the establishment of general physical realization criteria. Finally, it remains to relate the response of stepped systems to a more general smoothly varying system.
Speed of Sound in Heavy Water as a Function of Temperature and Pressure
Authors: Wilson Wayne D.
Published: September 2005

The speed of sound has been measured in heavy water, D2O, by a pulse technique. An equation is presented to express the results of these measurements in analytic form and is used to compute tables of sound speed in D2O. A comparison of the sound speeds in D2O at atmospheric pressure obtained by an optical method, an interferometer method, and the present pulse method is made. The results from the pulse method and the optical method agree within the experimental error; however, the interferometer method gave higher sound speeds than the other two.
Sonic Images
Authors: Suckling E. E. , McLean W. R.
Published: September 2005

This paper presents pictures of various objects which have been obtained by the authors using ultrasound instead of light as illumination. Reference is gives to previous papers which described the basic method. Subsequent modifications to the original method are described.
Vibrational Modes on Barium Titanate Ceramic Disks
Authors: Martner J. G.
Published: September 2005

A means of observing high-frequency vibrational modes on barium titanate ceramic disks has been developed, utilizing Bernoulli attraction forces in a liquid suspension of fine particles, patterns for vibrational modes covering the frequency band of 80 kcps to one megacycle and higher have been obtained.
Exact Solution of Wave Scattering by Irregular Surfaces
Authors: Marsh H. W.
Published: September 2005

The problem which Lord Rayleigh considered (reflection from a corrugated surface) and which several have treated approximately in recent years, is developed in a general form. An exact solution is obtained by extensive use of Wiener's generalized harmonic analysis. This solution is readily extended to include electromagnetic waves, general elastic waves, and nonplanar, nonharmonic sources. Numerical evaluation of the formulas is considered by means of an operational representation, from which various types of successive approximations can be constructed. Applications can be of special interest in scatter communications and in underwater sound transmission and reverberation. Experimental evidence from the latter area indicates that a rather detailed theory is necessary for an adequate account of the situation.
Scattering of Underwater Sound by the Sea Surface
Authors: Marsh H. Wysor , Schulkin M. , Kneale S. G.
Published: September 2005

A theory is presented of the scattering of underwater sound by the sea surface. The Neumann-Pierson oceanographic model of the sea is used. These developments are applied to propagation in an isothermal surface-bounded channel. A theoretical curve is presented of surface loss vs the rms wave height and frequency product at the lower end of the curve.
Visual Indication of Speech as an Aid to Hearing It in Noise and Babble
Authors: Decker Louis R. , Pickett J. M.
Published: September 2005

Intelligibility tests were conducted to determine whether watching a visual indication of a speech signal would improve its intelligibility under conditions of low signal-to-noise ratio. Noises were tested which had different amounts of similarity to speech. The visual indication was presented on a VU meter. It was found that there is no improvement in intelligibility associated with this type of supplementary visual information.
Pitch Sensation and Its Relation to the Periodicity of the Stimulus. Hearing and Skin Vibrations
Authors: v. Békésy Georg
Published: September 2005

It has been suggested that the nervous system of the ear is capable of identifying the periodicity of a complex sound, as such, isolated from other factors. Because many phenomena in hearing have their counterparts in the vibratory sensations of the skin, the question is analyzed whether the skin also is able to identify and isolate periodicity of the stimulus. Since a phenomenon described by Seebeck 100 years ago seems to provide the best demonstration of periodicity perception in hearing, an analogous phenomenon the skin has been investigated for both mechanical and electrical stimulation. The skin too showed the Seebeck phenomenon. But it became obvious that on the skin it is possible to change the periodicity without altering the “pitch sensation” or to change the pitch sensation without having modified the periodicity. The pitch sensation for complex sounds and complex vibrations is probably not a simple process.
Simultaneous Dichotic Frequency Discrimination
Authors: Odenthal D. W.
Published: September 2005

It is found that in the frequency range below 1000 cps, an approximately constant frequency difference (11–14 cps) is needed to obtain a just noticeable interaural difference in pitch; between 1000 and 1500 cps the limen rapidly increases. At 1500 cps, it amounts to some 60–75 cps, or 4–5%. The percentage sensitivity then remains constant up to some 2400 cps. Between 2400 and 3000 cps there is a second sharp rise of the limen, which reaches a value of 300 cps (or 10%) at the latter frequency. Between 3000 and 8000 cps, the percentage sensitivity remains constant at about 10%.
Vowel Recognition Using a Multiple Discriminant Function
Authors: Smith J. E. Keith , Klem Laura
Published: September 2005

An application of statistical detection theory to automatic speech recognition is presented. The multiple discriminant function approach is applied to the problem of vowel recognition. Twenty-one speakers, 10 females and 11 males, produced 215 single vowel words, exemplifying ten different vowels. The linear discriminant function correctly labeled 87% of the utterances; the quadratic discriminant function correctly labeled 94%. It is pointed out that these detections were achieved without use of duration information and without explicit use of formant information.
Long-Range Measurement of Sound Speed in Sea Water
Authors: Garrison G. R. , Kirkland P. C. , Murphy S. R.
Published: September 2005

Measurements of the speed of sound in sea water by transmitting sound pulses a distance of 1000 yards are in agreement with the +0.2% correction to the Kuwahara tables recommended by Del Grosso and Wilson.
Wave Propagation in Elastic Plates: Low and High Mode Dispersion
Authors: Tolstoy Ivan , Usdin Eugene
Published: September 2005

This is an analysis of dispersive properties of elastic plates in vacuo. For low modes there exists conclusive experimental verification of these properties. Model studies show prominent arrivals having the proper spectra and velocities for group velocity maxima and minima corresponding to several symmetric and anti-symmetric modes. In addition, detailed calculations based upon exact formulas predict some new and as yet unconfirmed properties of plates, e.g., negative phase velocities. New results concerning high modes of propagation are also displayed. These modes are of considerable theoretical interest since they belong to the transition region between the domains of validity of the wave and ray theories. The structure of the symmetric and antisymmetric fiftieth mode dispersion curves illustrates that for a given angle of incidence the propagating energy will be either chiefly shear or chiefly compressional, passage from one to the other corresponding to energy transfer between symmetrical and antisymmetrical modes or propagation. Comparison with multilayered liquid wave guides are mentioned.
Flexural Waves in Elastic Beams of Circular Cross Section
Authors: Abramson H. Norman
Published: September 2005

The exact equations of elasticity are employed in an investigation of the flexural vibrations of a solid circular cylinder. Contrary to previous work, it is shown that the phase-velocity-wavelength relation has an infinity of branches, thus overcoming objections, on physical grounds, which have been made to the earlier work. The three lowest branches of this dispersion relation are calculated, and these are used to study the rate of energy transmission in terms of group velocity.
Scattering in an Inhomogeneous Medium
Authors: Skudrzyk Eugen
Published: September 2005

The standard mathematical procedure formally describes scattering by the superposition of a scattered pressure on the unscattered sound field. At low frequencies, because of the irregular distribution of the inhomogeneities, the phases of the scattered waves are at random and scattering is an interference phenomenon. As the frequency increases, scattering becomes highly collimated in the forward direction and the phase differences decrease to zero. At this point ray theory starts to apply. The scattered pressure, then, essentially describes only a phase change caused by the different sound velocities and the focusing and defocusing by the lens action of the patches.

The medium in the neighborhood of the receiver can be shown to contribute only by focusing, the medium farther away only by interference fluctuations. Focusing leads to normally distributed amplitude fluctuations. The distribution of the interference fluctuations, however, passes from normal to Rayleigh with increasing values of range.
Preliminary Measurements on the Viscoelastic Properties of Animal Tissues at Audio-Frequencies
Authors: Fitzgerald Edwin R. , Ackerman Eugene , Fitzgerald James W.
Published: September 2005

In this preliminary investigation the electromagnetic transducer method of Fitzgerald and Ferry is used to obtain the complex shear compliance and shear modulus of muscle tissue taken from a freshly killed cow at room temperatures and in a frequency range from 25 to 2500 cps. Both the level and the shape of the compliance-frequency curves are found to depend on the elapsed time after slaughtering. While there are some difficulties due to the rapid changes in viscoelastic properties with time, the results indicate that the method can be successfully applied to determine the viscoelastic properties of animal tissues.
Refraction of Underwater Explosion Shock Waves by a Strong Velocity Gradient
Authors: Brockhurst R. R. , Bruce J. G. , Arons A. B.
Published: September 2005

The effects of a strongly refracting summer thermocline on the initial pressure pulse from an underwater explosion were accurately measured in a flooded quarry. The familiar exponentially decaying pulse shape was observed to be drastically altered in highly divergent regions of the field. Closely spaced measurements permitted these shape changes, as well as the increased amplitude and decreased time constant in a caustic region, to be followed continuously from the source. It is presently impossible to compute the observed pulse shapes although measured shock pressures agreed well with ray-theory predictions except near the caustic. Measured travel time differences between initial arrivals and both second direct arrivals and surface reflections agreed quite exactly with predictions.
Effect of the Splayed Walls of a Room on the Steady-State Sound Transmission Characteristics
Authors: Nimura Tadamoto , Shibayama Kimio
Published: September 2005

The steady-state sound transmission characteristics in model rooms of various shapes were measured. The shape of the model was varied from rectangle to trapezoid and to quadrangle with nonparallel walls, while the interior volume of the room was kept constant. In the results, it was observed that the trapezoidal rooms in which the ratio of l to a is about 10%, where a is the mean length of the parallel walls, and l is the difference between them, are effective in decreasing frequency irregularity in the transmission characteristics.

On the other hand, the sound characteristics of a fan-shaped room, adopted as an example of splayed rooms, were analyzed mathematically. The fan-shaped room with ρ0≃1.2∼1.4 has good characteristics in low-frequency region, where ρ0 is the ratio of the outer and inner radius of the room. Such a fan-shaped room corresponds to a splayed room with l/a≃0.09∼0.17. The results are in good agreement with the experimental results and our experience.
Acoustic Intensity Anomalies Introduced by Constant Velocity Gradients
Authors: Pedersen Melvin A.
Published: September 2005

This paper demonstrates by theoretical and numerical examples that in the calculation of ray-theory intensities in an underwater sound field the use of constant gradient layers can introduce spurious caustics and in some cases can omit real caustics. The theoretical intensity is discontinuous and becomes zero for a ray which is horizontal at any layer interface where the slope of the velocity-depth function is discontinuous, not only for constant gradient layers but for any function which might be used to approximate the profile. If the slopes as well as velocities are continuous at a layer interface, the intensity will generally be continuous. The use of curved line segments preserving both velocity and slope continuity in the profile approximation is suggested.
Orchestra Enclosure and Canopy for the Tanglewood Music Shed
Authors: Johnson F. R. , Beranek L. L. , Newman R. B. , Bolt R. H. , Klepper D. L.
Published: September 2005

The Tanglewood Music Shed, a large fan-shaped hall seating 6000 people indoors (approximately 6000 more can be accommodated outdoors on the lawn) was modified in 1959 to improve the acoustics. The acoustical qualities that were to be improved included sectional balance for large orchestra, balance between orchestra and soloist, clarity of music inside the hall, and loudness of music on the lawn. The architectural solution was the design of an orchestra enclosure and a canopy over the orchestra and the front part of the audience. Also, a 14-ft high chamber music orchestra enclosure was installed in 1960. This paper discusses the details of the construction and presents comments by musicians and listeners following its completion.
Loudness Summation under Masking
Authors: Scharf Bertram
Published: September 2005

The loudness of four-tone complexes centered at 250, 2000, and 4000 cps was measured as a function of the over-all spacing, ΔF, of the components, both in the quiet and against various levels of a uniform masking noise. When the masking noise was held at a constant level, the loudness of the complex increased more with ΔF at moderate sensation levels—between about 30 and 60 db—than at either higher or lower levels. Near the masked as well as the absolute threshold, the loudness decreased as ΔF was increased beyond the critical bandwidth. Only when ΔF was less than a critical band, was loudness independent of ΔF and was the amount of loudness summation invariant with level. These results support the hypothesis that the amount of loudness summation depends upon the slope of the loudness functions for the individual critical bands that form the complex.
Noninteraction of Temporary Threshold Shifts
Authors: Ward W. Dixon
Published: September 2005

A 1-hr exposure to a high-frequency noise (2400–4800 cps at 100-db SPL) was (a) preceded or (b) followed by a 1-hr exposure to a low-frequency noise (600–1200 cps at 110-db SPL). Although both noises produced considerable temporary threshold shifts at frequencies just above the corresponding noise frequency, neither had any effect on the growth or recovery of shifts produced by the other. It is concluded that the course of the fatigue process at one area of the basilar membrane is relatively independent of conditions existing at other areas.
Interferometric Determination of Ultrasonic Absorption in Castor Oil
Authors: Schuele D. E. , Gutowski F. A. , Carome E. F.
Published: September 2005

Observations have been made of the absorption of ultrasound in castor oil at 3 Mc over the temperature range from 10° to 45°C. An improved interferometer system which utilizes a liquid-to-air reflecting interface was employed, together with a simplified electrical detection circuit. The observed absorption is less than the classical values below 25°C, but greater at higher temperatures. In general, the results compare well with those obtained by other observers using different measuring techniques.
Use of Piezoresistive Materials in the Measurement of Displacement, Force, and Torque
Authors: Mason W. P. , Thurston R. N.
Published: September 2005

The use of piezoresistive materials as strain gauges and in the measurement of displacement, force, and torque is discussed generally. A torsional transducer which has been constructed from n-type germanium is described, and the experimentally obtained voltage-torque characteristic given.
Nonaxially Symmetric Motions of Cylindrical Shells
Authors: Mirsky I. , Herrmann G.
Published: September 2005

A Timoshenko-type theory of cylindrical shells, developed by the authors in a previous paper [G. Herrmann and I. Mirsky, J. Appl. Mech. 23, 563–568 (1956)] for the case of axial symmetry, is generalized presently to include nonaxially symmetric motions. As an application, the propagation of free harmonic waves in the axial direction of a shell of infinite extent is studied and discussed in the light of previous work on this problem.