bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimum Hydrophone Design for Low Frequencies
Authors: Hueter T. F. , Moose P. H. 
Published: September 2005

In a recent paper, P. M. Kendig emphasizes the importance of efficiency in the design of an optimum hydrophone. However, in most applications, the threshold of signals that may be measured is determined essentially by the self-noise of the associated preamplifier. Therefore, in practice, the highest sensitivity hydrophone will result in the best signal-to-noise ratio.
Because of the availability of high-grade ceramics and high-impedance preamplifiers. the significant problem facing the designer is which physical configuration to employ. The comparative equations of Table I of the reference paper may be misleading in the selection of the optimum physical shape, which, as demonstrated by a practical example, should be dependent on consideration of sensitivity and impedance.
Backscattering of Sound from the Sea Surface: Its Measurement, Causes, and Application to the Prediction of Reverberation Levels
Authors: Urick R. J. , Hoover R. M. 
Published: September 2005

In many applications of underwater sound, the “reverberation,” or backscattered return, from the sea surface is the limiting background in which the desired echo appears. Little has been known about sea-surface backscattering in spite of its importance to the prediction of reverberation levels in practical applications.
Using two transducers—one for transmitting, one for receiving—mounted so as to be rotatable in a vertical plane and suspended from a buoy, measurements have been made of the backscattering of sound pulses from the surface of the sea as a function of grazing angle between 5 and 90 degrees, wind speed between 3 and 18 knots, and pulse length. When converted to a scattering coefficient per unit area, the results provide some hints as to the processes by which sound is scattered by the ocean surface, and give the basic data for computing the reverberation to be expected with transducers of arbitrary beam width and orientation.
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.
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.
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?
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.
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.
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.
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.
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.
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.
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.
Perturbations in Vocal Pitch
Authors: Lieberman Philip 
Published: September 2005

An acoustic analysis of the rapid fluctuations that occur in the fundamental excitation rate, or “pitch,” of normal speech was conducted with a sample of six male speakers of American English, who each read a neutral test sentence in certain “emotional” modes. i.e., as a question, an objective statement, a fearful utterance, a happy utterance, etc. A statistical analysis of the durations of approximately 7000 pitch periods was performed with an IBM 709 computer. This analysis revealed that for all possible samples consisting of three consecutive periods, the duration did not remain constant, within ±0.1 msec, in 86% of the cases. The data also showed that the magnitude of the difference between the durations of adjacent periods was greater than 0.6 msec 20% of the time and greater than 1.0 msec 15% of the time. The magnitude of this difference increased with the duration of the periods until their duration reached 6 msec. The difference was independent of the period duration for periods longer than 6 msec. Somewhat greater differences between the durations of successive periods occurred in those samples associated with the onset and end of voicing and sudden spectral shifts. Smaller differences occurred with certain of the emotional modes that seemed to require greater conscious vocal control in their production.
The output of the glottis often seemed to be like that of an oscillator with considerable overshoot. In 38% of the cases it produced a sequence of alternately short and long duration periods. The durations of adjacent periods were not correlated. The durations of alternate long and alternate short periods, however, were highly correlated, suggesting a hysteresis effect in which the duration of each period is determined with respect to the preceding period in a quasi random manner within a 2-msec range.
Peak Criterion in Random vs Sine Vibration Testing
Authors: Spence H. R. , Luhrs H. N. 
Published: September 2005

Sinusoidal vibration has practical value as a substitute for random vibration in equipment qualification testing. How and when to employ a sinusoidal substitution is discussed in this paper. In particular, a damage criterion is discussed, which relates the number of sinusoidal peaks occurring while passing through a resonance to the number of random peaks exceeding a specified amplitude value.
Formulas are given for the sine-random response relationship, with formulas and a diagram for the random test duration to be used with the amplitude relationship.
Background Information on the Activities of Committee Z24-W-18, Sound Level Meters
Authors: Hardy Howard C. 
Published: September 2005

This symposium on sound level meters is essentially a report of Committee Z24-W-18 of the American Standards Association, which for three years has been evolving a new standard for sound level meters. This new standard is more than a revision of the current one (Z24.3-1944), since early in the deliberations of the committee it was decided that the standard warranted a completely new draft.
All persons participating in the symposium are either members of Committee Z24-W-18 or have been closely associated with the committee activity. In addition to the participants, other committee members have done yeoman work in the preparation of the draft through its numerous revisions. These other members are Mr. George Bonvallet, Dr. Arnold Peterson, Dr. Paul Veneklasen, Dr. Richard Wells, and the late Dr. Paul Geiger.
Elastic Wave Dispersion in a Cylindrical Rod by a Wide-Band Short-Duration Pulse Technique
Authors: Oliver Jack 
Published: September 2005

Dispersion of elastic waves in a cylindrical rod, determined experimentally by means of a wide-band short-duration pulse technique, compares well with theoretical curves of the classical theory. This method, compared to previous methods, extends to smaller values the range of the wavelength to diameter ratios which may be studied conveniently.
One antisymmetric and two symmetric modes were studied. In addition, waves of a resonant nature associated with the ends of the rod were identified.
Concerning the Fundamental Component of Periodic Pulse Patterns and Modulated Vibrations Observed on the Cochlear Model with Nerve Supply
Authors: v. Békésy G. 
Published: September 2005

Seebeck demonstrated that there are series of clicks for which Fourier analysis shows a very small fundamental component or none at all, in spite of the fact that a distinct tone complex close to the fundamental component can be heard. Similarly, in a modulated tone, the modulation frequency as such may be heard without being present in the Fourier analysis.
This paper shows that on the model of the cochlea the artificial basilar membrane vibrates at the place corresponding to the absent fundamental or the modulation frequency. The vibration seems to be a consequence of the complicated traveling-wave patterns and their interferences. This may be of interest for some hearing theories.
Overstimulation, Fatigue, and Onset of Overload in the Normal Human Ear
Authors: Lawrence Merle , Yantis Phillip A. 
Published: September 2005

Studies on the effect of overstimulation upon the ear have been handicapped by lack of an audiometric procedure known to detect subtle changes in the organ of Corti. Fatigue has often been suggested and used but studies of the cochlear potentials associated with low-intensity vibration of the organ of Corti have never revealed such fatigue, which must arise from more central structures. Fatigue following high levels of sound intensity is probably a sum of “neural” fatigue and an injury to the organ of Corti. On the other hand, such studies have shown aural overload to result from an overdriving of the organ of Corti beginning at an intensity of sound considerably below that which is injurious.
The experiments reported here compare the shift in audibility threshold and in onset of overload following one-minute stimulations with a 1000-cps tone at sensation levels of 20, 60, 80, 90, 100, and 110 db. The amount of post-stimulus fatigue measured 6 seconds after cessation of the fatiguing tone showed little variation with intensity of fatiguing tone whereas the onset of overload, when compensation was made for fatigue of the harmonic frequency, showed a progressive lowering with increase of intensity of fatigue tone.
It is concluded that within the limitations of these experimental conditions the fatigue measured is not a property of the sensory cells whose sensitivity does not change until an injurious level of tone is reached, but that overloading is a property of these cells and the lowering of its onset level reflects an increasing decrement in performance following increasing intensities of stimulation.