bluuebunny/crossref_metadata_2025 huggingface dataset:
Masking Patterns of Tones
Authors: Ehmer Richard H.
Published: September 2005

Monaural masking patterns were obtained for pure tones spaced by octaves from 250 cps to 8000 cps at 20–100 db SL on three listeners in an attempt to provide extensive data assessing the relative importance of aural harmonics and cochlear spread of masking tone activity in the extension of masking to frequencies above the masking tone. The masking patterns confirm and extend the results of others, but especially indicate that second peaks do not necessarily occur at the second harmonic of the masking tone. The masking patterns are explained in terms of (1) the activity pattern of the masking tone in the cochlea, (2) beats between signal and masking tones, (3) aural harmonics, and (4) suppression of cochlear response to the signal.
Relation between Loudness and Duration of Tonal Pulses. I. Response of Normal Ears to Pure Tones Longer than Click-Pitch Threshold
Authors: Miskolczy-Fodor F.
Published: September 2005

In normal ears, threshold intensity as a function of the duration of a tonal pulse is determined. Identical results are obtained by a reciprocal determination. The reciprocal determination is made by fixing the intensity level at specified points above reference threshold to measure the time threshold. The duration-intensity relationship reveals a marked dependency upon frequency; the differences observed are equivalent to the alteration of loudness function for the various test frequencies. A new measure of loudness increment degree, as well as conversion of decibel values into phon and sone values, indicates a close relationship between time threshold and loudness sensation. Therefore, the relationship between pulse duration and loudness level presents no artifacts reflecting frequency-dependent changes. The time threshold (T msec), as a fraction of pulse duration re the “adjusting time” of the auditory mechanism (150/T), seems to indicate the loudness of related levels above threshold in sones. General conclusions deriving from these relationships and some limitations of their applicability are discussed in detail; these are confirmed by a comparison between monaural and binaural time-threshold measurements.
Low-Frequency Noise and Methods for Calculating Speech Intelligibility
Authors: Pickett J. M.
Published: September 2005

Speech intelligibility was tested in a low-frequency masking noise. Various conditions of speech and noise filtering below 1200 cps were employed in order to test the relative effects of direct low-frequency masking and upward spread of masking to higher frequency regions. Tests were carried out at three noise spectrum levels which corresponded to overall unfiltered levels of 85, 105, and 115 db. The results showed significant decreases in intelligibility as the noise energy was admitted progressively between 300 and 20 cps. Further, the speech frequencies between 20 and 300 cps provided no significant contribution to intelligibility under any noise condition tested. It is, therefore, concluded that the low frequency energy in the noise produced upward spread of masking. This interpretation is reinforced by the fact that spread of masking was greater at higher noise levels and also at lower speech-to-noise ratios. Implications for calculating the effects of noise interference upon intelligibility are discussed.
Note on Finite Amplitude Propagation Effects on Shock Wave Travel Times from Explosions at High Altitude
Authors: Reed S. G.
Published: September 2005

Consequences are given of taking into account energy loss, in addition to lengthening of the overpressure phase, of a weak shock wave traveling vertically downward in an exponentially stratified atmosphere.
Measurements of the Backscattering of Underwater Sound from the Sea Surface
Authors: Garrison G. R. , Murphy S. R. , Potter D. S.
Published: September 2005

Measurements of the backscattering of 60-kc sound from the surface of the sea have been made in Puget Sound in an effort to relate the strength of the scattered sound to the character of the surface. In addition to providing a means of predicting reverberation levels, an attempt has been made to obtain a better understanding of the fundamental mechanism of scattering at the air-water boundary.

The reverberation measurements are presented, along with observations of several oceanographic and meteorological parameters. An examination of the data allows the following conclusions: (1) reverberation pulses from an area of several square yards follow a Rayleigh distribution; (2) reverberation cannot be directly related to the wave height, but is closely correlated with wind speed; (3) reverberation increases with wind speed to a speed of 14 knots, and remains constant for higher wind speeds; and (4) reverberation is independent of the angle with the surface for angles from 20 to 60 degrees, but drops off rapidly as the angle is decreased below 20 degrees.
Kinetics of the Decolorization of Congo Red under Ultrasonic Radiation
Authors: Prakash Satya , Prakash Sheo
Published: September 2005

The fading of the color of the congo red dyestuff at concentrations 0.016. 0.01, and 0.005 g per liter under the influence of ultrasonic radiation from a Mullard generator with barium titanate crystal having a frequency of 1 Mc/sec and power output 225 w has been studied and the reaction is found to be unimolecular, the average velocity constants being respectively, 0.129, 0.209, and 0.193. The fading of congo red is not due to the production of hydrogen peroxide, and it is neither an oxidation nor a reduction process in the ordinary sense. The high cavitation energy appears to be responsible for the breaking down of the molecule of congo red resulting in the color fading.
Noise Production in a Turbulent Boundary Layer by Smooth and Rough Surfaces
Authors: Skudrzyk E. J. , Haddle G. P.
Published: September 2005

In a turbulent boundary layer, the effective velocity fluctuations amount to about 4% of the free-stream velocity, independent of the curvature of the body and within wide limits independent of the velocity of the flow. The fluctuations in pressure can then be computed from those of the velocity by an equation similar to the standard Bernoulli equation, except that the numerical constant is different. Vortices pass along the receiving hydrophone; they represent pressure pulses that generate a constant power spectrum at low frequencies that decreases approximately inversely proportional to the cube of the frequency at higher frequencies. This information, in conjunction with the pressure equation, makes it possible to compute the power spectrum of the flow noise as a function of the frequency, the boundary layer thickness and the speed of the flow. The flow noise at greater speeds and at higher frequencies turns out to be predominantly generated by the surface roughnesses.

A small hydrophone records the local fluctuations at the pressure in the boundary layer; on the other hand, a large hydrophone is very insensitive to the small-scale turbulence. It indicates the true sound pressure that is produced by the generation and the decay of the turbulence and by the vibrations of the walls of the vessel. A large hydrophone therefore reads the same pressure, whether it is placed inside the boundary layer or outside the near field region, not too far away from the turbulent layer. The theoretical conclusions are borne out, qualitatively and quantitatively, by the experimental results obtained with the aid of a rotating cylinder and through measurements in the test section of the Garfield Thomas Water Tunnel.
Space Requirements for Simple Mechanical Systems Excited by Random Vibration
Authors: Himelblau H. , Keer L. M.
Published: September 2005

The problem of collision between a simple mechanical oscillator (with damping) and an adjacent rigid member, or between two adjacent simple oscillators, when both are subjected to random vibration is solved in terms of probability of occurrence and the mean time between occurrences. A complete solution is obtained for white Gaussian excitation. This solution can be applied to such problems as the mechanical design of electronic components, bottoming of resilient mounts, and collision between an equipment item and adjacent structure, when the representations of a single degree of freedom system can be used.
Effects of Ultrasonic Irradiation on Hemoglobin
Authors: Weissler Alfred
Published: September 2005

Oxyhemoglobin in dilute aqueous solution is rapidly converted by ultrasonic irradiation into methemoglobin, which in turn is gradually destroyed, as shown by the disappearance of its optical absorption peak at 4050 A. Hematoporphyrin similarly suffers partial destruction by ultrasound. On the basis of experiments in various chemical environments, the previous results are ascribed largely to the nitrous and nitric acids produced by ultrasonic cavitation in water containing dissolved air. Adding 0.1 ml ether/25 ml of solution causes the sonochemical change to be from oxyhemoglobin into carboxyhemoglobin, instead of into methemoglobin. Ultracentrifuge studies indicate that ultrasonic treatment of hemoglobin in more concentrated solution also causes some splitting off of the heme from the globin. A comparison of the reported effects of x rays on hemoglobin with those found for ultrasound shows that there are differences as well as similarities. The ultrasonic frequency used was 400 kc per sec, and the acoustic power delivered into the reaction vessel in a focused beam was about 20 w.
Ultrasonic Measurement of Vibrational, Rotational Isomeric, Structural and Shear Relaxation in Isobutyl Bromide
Authors: Clark A. E. , Litovitz T. A.
Published: September 2005

Ultrasonic measurements of the longitudinal absorption and velocity and shear impedance were made over a large range of temperatures in the weakly associated liquid isobutyl bromide. Evidence was found for the coexistence of four different relaxation mechanisms. Above −50°C rotational isomeric relaxation exhibiting a single relaxation time was found. Vibrational relaxation also appears to be present with a relaxation time shorter than that usually found in nonassociated liquids. The dispersion and absorption data below −125°C showed that both shear and structural relaxation effects were present. The former was related to a distribution of relaxation times. The coexistence of these several relaxations is consistent with the concept that a weakly associated liquid should show relaxation behavior typical of both strongly and nonassociated liquids.
Transverse Oscillations of a Liquid Jet. I
Authors: Brackenridge J. Bruce
Published: September 2005

Observations have been made of a thin rectangular jet which issues from an orifice and impinges upon the apex of a rigid wedge which is parallel to the plane of the jet. Such a system displays steady motion or motion corresponding to one of a unique set of ordered oscillatory modes. Which state of motion occurs at a given time depends upon stream thickness, orifice-to-edge distance, stream velocity, kinematic viscosity, and the previous history of the jet. The investigation is divided into two main parts. One deals with the ranges of parameters of the system for which it will execute self-maintained oscillations of a given mode; the other treats frequency characteristics for the different modes. It is found that self-maintained oscillations exist in fluids with a wide range of viscosity. The frequency characteristics are obtained by both optical and acoustical methods; an empirical formula for the frequency is developed.
Moment Impedance of Plates
Authors: Dyer Ira
Published: September 2005

The moment impedance of an infinitely extended plate is calculated with the use of plate equations that allow for transverse shear deformation and rotatory inertia. It is shown that the effects of transverse shear deformation may be important even for thin plates, a result that is not contained in classical theory. Classical theory is shown to be inadequate when the distance over which the moment is applied is smaller than plate thickness. The moment impedance for geometries of greatest practical interest is found to consist of a resistance connected in series with a stiffness reactance, both roughly inversely proportional to frequency, with the reactance of greater magnitude. Both the resistance and the reactance decrease with decreasing distance over which the moment is applied, because of the increasing importance of transverse shear flexibility. The practical implications of the results are discussed, and some thoughts are given concerning other problems where classical theory for flexural waves in thin plates may not be applicable.
Dependence of Mechanical Q and Young's Modulus of Ferroelectric Ceramics on Stress Amplitude
Authors: Gerson Robert
Published: September 2005

In this work the effects of stress amplitude on the mechanical properties of several barium-titanate and lead-titanate-zirconate compositions were studied. The mechanical Q was found to decrease to about 13 of its low-signal value at a dynamic stress of about 1500 psi. No further decrease occurred with stress up to about 4000 psi, the limit of these tests. Young's modulus decreased by about 5% in materials used in power transducers, and by about 25% in special compositions having low coercive force. It is concluded that the mechanical quality at the highest stress amplitude is still sufficiently high so that it will not seriously affect the efficiency of a well-matched acoustic transducer.
Monaural Temporal Masking Investigated by Binaural Interaction
Authors: Guttman Newman , van Bergeijk W. A. , David E. E.
Published: September 2005

Three experiments were conducted to study monaural temporal masking as manifested in binaural interactions. The experimental paradigm consisted of presenting a pair of clicks in one ear and a single “probe” click in the other. The ability of listeners to bring the probe click into fusion with one or the other contralateral click served as the principal measure of masking. Forward masking (inability to fuse the second click) was studied as a function of repetition rate and click levels. The forward-masking interval increased with increase of first-click intensity and, notably, decreased with increase of repetition rate. For the conditions and procedure of this experiment, the longest forward-masking interval was about 7 msec. Backward masking (inability to fuse the first click) appeared when the monaural clicks were proximate (up to 2 msec in this experiment) and the second click was much more intense than the first. This type of backward masking was deemed a short-term effect and was distinguished from long-term backward masking. A model is presented to account for the improved resolution at high repetition rates.
Vibrations of Thick-Walled Hollow Cylinders: Exact Numerical Solutions
Authors: Bird J. F. , Hart R. W. , McClure F. T.
Published: September 2005

The plane-strain vibration frequencies of an infinitely long hollow cylinder are calculated exactly with the aid of a high-speed electronic computer for a range of wall thicknesses and azimuthal node numbers and for a variety of boundary conditions. These latter cover the cases: outer radial surface free, supported, or clamped; inner surface free, supported, or matched to a gas filling the inner cavity. In the last case, we calculate the attenuation of sound in the cylinder wall, in addition to the eigenfrequencies. Our computations of mode frequencies disclose that: (i) the shear-compressional wave coupling in the solid is very weak (except for low frequency); (ii) for the gas-filled cylinder, the modes are very close either to the gas quasi-modes (gas in a rigid-walled cylinder), or to the solid quasi-modes (shell with free inner surface), depending on the geometry.
Some Results of Experiments Relating to the Generation of Noise in Jets
Authors: Lassiter L. W. , Hubbard H. H.
Published: September 2005

Some sample experimental results relating to the nature and sources of noise in jets are presented. Previous work is extended to include more detailed information about the jet structure. In this regard noise data are compared for jets having somewhat different turbulence profiles. High temperature jets are noted to have different radiation patterns and to be more efficient noise radiators than low temperature jets. Noise data for the high temperature supersonic jet of a rocket engine are included for comparison with those of subsonic jets. Some experiments have shown the noise levels at the low frequencies can be markedly reduced by the use of grids in the jet stream.
On the Spectrum of Noise from Turbulence
Authors: Mawardi Osman K.
Published: September 2005

An approximate method is developed for the estimation of the acoustic power frequency spectrum of the sound generated from isotropic turbulence. The method is based on a hypothetical model for the sound sources, originally produced by Lighthill, consisting of an assembly of quadrupoles extending over the region of turbulence.
Spoken Digit Recognition Using Time-Frequency Pattern Matching
Authors: Denes P. , Mathews M. V.
Published: September 2005

A study of the machine recognition of the spoken digits zero through nine has been carried out by a digital computer simulation. The spoken utterances were converted to time-frequency patterns of spectral energy. Recognition was done by cross correlating the pattern of an unknown utterance with a test pattern for each digit and selecting the digit having the highest correlation. Time normalization could be applied to all patterns, thus reducing utterances to a standard duration. Six male and one female speakers provided 38 samples of each of the 10 digits. Pauses were made between successive words for segmentation.

No errors were observed recognizing a single speaker using test patterns from his own speech with time normalization. A group of five male speakers and test patterns averaged over the group produced 6% errors with time normalization and 12% without. A 25% rate occurred for the woman matched against male patterns.

The study indicates both the effectiveness and limitations of this simple recognition procedure for limited vocabulary and limited number of speakers. Time normalization improves performance in all cases.
Absorption and Velocity of Ultrasonic Waves of Finite Amplitude in Liquids
Authors: Towle D. M. , Lindsay R. B.
Published: September 2005

This paper reports the results of measurements of the attenuation and velocity of ultrasonic waves in various liquid media as a function of the intensity level at the detector of the radiation. The attenuation in distilled water and dilute solutions of acetic acid and sodium acetate is found to increase almost linearly with the acoustic excess pressure amplitude in the range from 2 to 7 atmospheres, for frequencies of 4, 5, 7, and 9 megacycles/sec. The attenuation in glycerine shows a similar increase when correction is made for the unavoidable rise in temperature of the medium. The rate of increase is found to be practically independent of frequency in the range employed, thus disagreeing with the prediction of R. D. Fay's theory of the attenuation of high-amplitude plane waves. No change of velocity with source intensity has been observed.
Measurement of Perstimulatory Auditory Adaptation
Authors: Wright H. N.
Published: September 2005

The most frequently used estimate of perstimulatory auditory adaptation to a tone sustained in one (experimental) ear has been the intensity decrease at the contralateral (control) ear required for median-plane localization during successive 15-sec comparison intervals. Use of such a measure assumes that only negligible adaptation occurs in the control ear during these 15 sec. The results of this investigation show this assumption to be untenable. Adaptation in the control ear was measured by maintaining the experimental ear in an adapted state and then sustaining the comparison stimulus in the control ear. As the control ear adapted, the phantom sound associated with the tones to both ears moved toward the median plane. The time for this moving phantom sound to reach the median plane varied with the intensity and frequency of the comparison stimulus. The extent and rate of adaptation in the control ear was found to be such that all estimates of adaptation to tones sustained in the experimental ear are specific to the procedures used.
Ultrasonic Waves and Electrochemistry. V. The Frequency Characteristics the Electrokinetic and the AC Polarized Gas Electrode Effects
Authors: Saunders Frank , Yeager Ernest , Hovorka Frank
Published: September 2005

The frequency characteristics of the acousto-electrokinetic effect and the ac polarized gas electrode effect have been determined with pulse-modulated ultrasonic waves in the range 200 to 1000 kc/sec as a function of solution and electrode parameters. The electrokinetic effect involves the alternating potentials produced by acoustical waves on an electrode surrounded by a porous coveting in a dilute electrolyte while the ac polarized gas electrode effect involves the production of alternating components in the potential of a polarized electrode in an electrolytic solution with a gas such as hydrogen being liberated by a polarizing current. In the case of the electrokinetic effect, the open-circuit response relative to the pressure amplitude is inversely proportional to the frequency in very dilute solutions. The frequency dependence becomes considerably less with increasing conductance of the solution. The pressure response for the polarized hydrogen electrode also decreases with increasing frequency although the extent of the decrease is a function of current density and specific conductance. Both the response and stability of the polarized gas electrode have been greatly improved by the use of a directed flow of solution past the electrode to remove the cloud of gas bubbles in the bulk of the solution surrounding the electrode.

The mechanisms proposed for these effects in earlier publications have been further substantiated by the present work.
Thickness Measurement by Ultrasonic Resonance
Authors: Cook E. G. , VanValkenburg H. E.
Published: September 2005

A mathematical analysis made of the acoustic system of resonance-type instruments used for thickness measurements from one side only. The approach is general and can be used to evaluate any combinations of test sample, couplant, and driving crystal provided their acoustic properties are known. Correlation between the theory and experimental data is discussed. The results of the analysis have been used to compute thickness calibration screens and tolerances on components for a specified testing problem.
Zero Signals in the Sperry Tuning Fork Gyrotron®
Authors: Morrow Charles T.
Published: September 2005

The present paper provides a partial analysis of zero signals in the Sperry tuning fork Gyrotron, as produced by mass unbalance in the tuning fork, unbalance in the tuning fork drive, and asymmetry in the supports. The zero signal is shown to he highly independent of gravity and acceleration.
Analog Measurements of Sound Radiation from the Mouth
Authors: Flanagan James L.
Published: September 2005

Free-field measurements of the sound radiated from the mouth of a life-size mannequin are described. A transducer installed in the head of the dummy is calibrated to produce a known acoustic volume velocity at the lips. The sound field in vertical and horizontal planes through the head is explored with a pressure microphone. Measurements of pressure magnitude and phase are made for frequencies of 250, 500, 1000, 2000, and 4000 cps. The results are compared with the sound distributions for a simple spherical source, and for a small piston in a sphere of 9-cm radius. Over the frequency range investigated, and within a solid angle of about π sr centered on the mouth axis, the relations for the simple source are found to describe the measured magnitudes within approximately 3 db, and the measured phases within approximately 30 deg. The results are also compared with previously reported pressure distributions for speech. Some brief comment is devoted to approximating the radiation impedance of the mouth.
Variation of Acoustic Velocity with Temperature in Some Low Velocity Liquids and Solutions
Authors: Marks Graham W.
Published: September 2005

Acoustical velocities were measured at 500 kc in a number of organic liquids and binary solutions prepared therefrom. A precision ultrasonic interferometer was employed. For the most part sound velocities were found to vary linearly with temperature. Densities were determined at 20°C. Adiabatic compressibilities at 20°C were calculated and some conclusions drawn concerning the cohesive properties of certain of the solutions. The molecular sound velocity in a binary liquid solution is the sum of the products of the respective molecular sound velocities in the pure liquids by their corresponding mole fractions all at the same temperature. Where practicable, effective molecular radii were calculated from the data. The usefulness of the molecular weight of a liquid in predicting values of the temperature coefficient of velocity is discussed. Apparently many more experimental data are needed before an adequate theoretical analysis is possible.
On the Radiation Impedance of an Array of Finite Cylinders
Authors: Robey Donald H.
Published: September 2005

A general expression for the radiation impedance of the qth source in an array of n sources has been obtained in terms of Green's functions. It is applicable to finite sources or to sources which are mounted in finite baffles provided the Green's function can be found. The theory is applied to an array of finite cylinders which form part of an infinitely long rigid cylindrical baffle. If ka≪1, the radiation resistance of each member can easily be expressed in terms of sine integrals. Curves showing the radiation resistance of each member of an array of five cylinders are given. The effect of varying the separation is also shown.
On the Radiation Impedance of the Liquid-Filled Squirting Cylinder
Authors: Robey Donald H.
Published: September 2005

The impedance presented to the inside surface of a hollow, radially vibrating, liquid-filled cylinder of length ℓ which is mounted in the aperture of a rigid wall of thickness ℓ has been determined. It was assumed that radiation from the ends of the cylinder into the infinite liquid media (water) takes place symmetrically with respect to the plane midway between the ends of the cylinder. The liquid within the cylinder need not be the same as the liquid outside the cylinder. Although the impedance at any frequency can be obtained from the results, an approximation is introduced which is valid when the wavelength in the liquid within the cylinder is such that ka⩽π/2 (k being the wavelength constant and a the inside radius of the cylinder). Under these circumstances it is found that the output power drops to zero whenever the length of the cylinder equals nλ, where n is an integer and λ is the wavelength of sound in the contained liquid.
Effect of Duration on the Perception of Voicing
Authors: Denes P.
Published: September 2005

This paper describes an investigation of the effect of sound duration on the perception of a linguistic characteristic, the recognition of phonemes. A pair of single syllable words was selected which consisted of identical phoneme sequences, except for the final phoneme which was either the voiced or unvoiced version of the same articulation. Different versions of these words were synthesized with all possible combinations of four different vowel durations and five different final consonant durations. In all cases the sound wave corresponding to the final consonant was inharmonic and identical except for duration. These synthesized words were recorded and presented to a group of 33 listeners who had to judge whether they heard the final consonant as a voiced or as an unvoiced sound. The results clearly show that the relative durations of vowel and final consonant can be used as a cue for hearing the final sound as voiced or unvoiced. This demonstrates that, in certain circumstances, nonspectral characteristics such as duration can serve as the basis for phoneme recognition. It also gives an example of a cue for sound recognition which, due to its relative nature, can be perceived only when it appears in a sequence of phonemes and not when the sound is pronounced in isolation.
Shearing Motion in Scala Media of Cochlear Models
Authors: Tonndorf Juergen
Published: September 2005

In 1953, Bekesy first reported the occurrence of shearing motion within the cochlear duct and furthermore the notion that it is this mode of motion which constitutes the adequate stimulus for the hair cells. There were two modes of shear motion: radially directed in the region proximal to the place of maximal amplitude of the traveling-wave pattern, and longitudinally directed distal to that point.

This phenomenon was studied in cochlear models. The envelopes over both modes of shear motion were found to be much smaller than that over the traveling-wave pattern. A simple explanation presented itself. The direction of the shearing motion in each domain coincides with the dominant curvature produced by the traveling waves in that section of the cochlear duct.

Earlier, it had been shown that under the effect of Bekesy's eddies, i.e., at higher driving amplitudes, the displacement pattern of the cochlear partition becomes asymmetrical. This asymmetry produces a dc-shift in both domains of shear motion: in an outward direction within the domain of radial shear and in an apical direction within the domain of longitudinal shear. However, when the round window was driven, both directions of the dc-components were reversed. The latter finding aided in establishing the causal relationship mentioned in the foregoing.
Articulation Scores for Two Similar, Reverberant Rooms, One with Polycylindrical Diffusers on Walls and Ceiling
Authors: Jeffress L. A. , Lane R. N. , Seay Frank
Published: September 2005

Two rooms of about the same dimensions, one a rectangular parallelopiped, and one having polycylindrical walls and ceiling, were measured for reverberation times and for speech articulation. No significant differences were found in either characteristic. Since one of the rooms should provide a more diffuse sound field than the other, it can be tentatively concluded that diffusion may have little influence on speech intelligibility. Both rooms exhibited rather poor articulation scores as might have been predicted from their reverberation times.
Scattering of Sound by Sound
Authors: Bellin J. L. S. , Beyer R. T.
Published: September 2005

An attempt was made to determine the presence of scattering resulting from the nonlinear interaction of two finite-amplitude sources, operating in water. Experiments were performed with two beams crossed at right angles and also in the nonperpendicular case, A detector crystal, tuned to the summation frequency (13.4 Mc) of the two sources (7.4 Mc and 6.0 Mc), and pivoted about a point above the interaction region, was used to investigate the scattered field. The results indicated no scattered sound above the noise level of the detection system. The lack of scattered sound is in agreement with the theoretical considerations of Westervelt, but is contrary to the predictions of Ingard and Pridmore-Brown.
Patterns of Injury Produced by Overstimulation of the Ear
Authors: Wever Ernest Glen , Lawrence Merle
Published: September 2005

Measurements of the cochlear potentials as recorded from the round window were carried out on a series of guinea pig ears to ascertain the effects of injury by overstimulation with various tones. The results showed general impairments of the responses after such injury. With rare exceptions, the maximum responses to any tone are much less impaired than the sensitivity, and the maximums are more seriously affected for the low tones. In general, these changes are independent of the frequency of the tone producing the injury.

These observations confirm those of earlier studies on the patterns of action of tones in the cochlea, and indicate that all tones when raised to extreme levels cause widespread damage to the hair cells. It is suggested that certain hair cells, which are normally involved in the peak actions of all tones, are particularly susceptible to damage by overstimulation.
Listening to Differentially Filtered Competing Voice Messages
Authors: Spieth W. , Webster J. C.
Published: September 2005

An attempt was made to improve listeners' ability to respond to one of two or more simultaneous or overlapping voice messages by differentially filtering the competing message channels.

The limits of satisfactory intelligibility of two digits and two International Civil Aeronautics Organization (ICAO) phonetic alphabet words in a message also containing an address were determined under various conditions of high- and low-pass filtering and speech-to-noise ratios (S/N). Within these limits, several amounts of filtering were tried in various combinations.

When performance on differentially filtered competing messages was compared with performance on unfiltered competing messages, it was found that differential filtering almost always improved performance. This was true regardless of whether it was the desired message that was filtered or whether it was one or more of the competing messages that was filtered, and the degree of filtering was relatively uncritical. High-pass cutoffs of 565, 800, or 1130 cps were about equally effective and were considerably better than high-pass cutoffs at or below 280 cps. Low-pass cutoffs of 1600, 1130, and 800 cps also improved performance substantially.
Side Scattering of Sound in Shallow Water
Authors: Urick R. J.
Published: September 2005

When a sound beam travels through the sea, it is scattered in all directions by inhomegeneities of various sorts in the sea and on its boundaries. In the backward direction, the aggregate of all the scattered contributions is called “reverberation.” In other directions, the “side scattering” can be studied by using two directional transducers, trained so that the beams cross each other, to measure the sound scattered out of one beam and received on the other. This method was employed in an off-shore area in the Gulf of Mexico having a particularly uniform bottom. Using two bottomed transducers a mile and a half apart, the intensity of scattering was measured at 22 kc for different angular orientations of the two beams. The measurements were reduced to the coefficient, scattering strength, without requiring either transducer calibrations or direct measurements of transmission loss.

The results indicate a bottom scattering strength between −30 and −40 db having no appreciable dependence on angle between the two beams. Within the angular range from the backward direction around to 150° in the forward direction, the scattering appears isotropic. This indicates that isotropic bottom scattering may be safely assumed in applications utilizing separated transmitting and receiving transducers at kilocycle frequencies.
General Theory for the Synthesis of Hydrophone Arrays
Authors: Heaps H. S.
Published: September 2005

An acoustic signal pressure and a noise background are supposed incident upon a general array of hydrophone elements whose individual outputs are combined in a linear manner by means of amplifiers and time delays. Determination is made of the optimum spatial distribution of the hydrophone elements, and also the optimum combination of their outputs, in order to produce in the combined output a maximum value of peak signal in relation to the average noise background. The incident signal is not restricted to be a continuous wave of a single frequency.
Dispersion and Simple Harmonic Point Sources in Wave Ducts
Authors: Tolstoy Ivan
Published: September 2005

In a previous article it was shown that if plane wave reflection coefficients were written as rotations, the characteristic equation for the normal modes could be expressed very simply by means of the arguments. The method is elaborated here for the case of multilayered media. Also, an exact and general solution the guided wave terms due to a simple harmonic point source in a duct is obtained. This is done by applying our characteristic equation to an integral solution due to Brekhovskih. A numerical example is given, illustrating quasi-resonance and anti-resonance phenomena associated with stationary values of the group-velocity under simple-harmonic conditions.
Production of Accelerated Cavitation Damage by an Acoustic Field in a Cylindrical Cavity
Authors: Ellis A. T.
Published: September 2005

A convenient and economical method for the production of cavitation damage is described. Cavitation is generated in the region of the maximum pressure amplitude of an acoustic field in a resonant cylindrical container. The specimen surface to be damaged is a stationary boundary in the system and is therefore not subject to accelerations such as occur in conventional magnetostriction devices for cavitation damage study. The absence of these accelerations eliminates any possibility of premature material removal from cavitation weakened surfaces. Mathematical analysis of the dynamics of cavitation should also be facilitated. It is shown that simple assumptions lead to an acoustical theory agreeing with experiment to within the accuracy required. Examples are given of the application of this technique to the study of both easily damaged and highly resistant materials. Relatively uniform damage is achieved which is particularly suitable for x-ray diffraction study of the surface. Alternatively, perturbation of the acoustic field to permit concentrated damage is obtained by forming the specimen surface as the end of a small cylinder. Photomicrographic studies of damage to both monocrystalline and polycrystalline materials have been initiated with the aid of this apparatus. Cavitation experiments have been done in water with an air atmosphere and in toluene with a helium atmosphere. These experiments show that severe damage can result even if a chemically inert environment is employed.
Theory of Vortex Whistle
Authors: Michelson Irving
Published: September 2005

The characteristic feature of B. Vonnegut's vortex whistle is the proportionality of pitch to flow rate [B. Vonnegut, J. Acoust. Soc. Am. 26, 18 (1954)], in contrast with more common types of whistles in which geometry determines the pitch. A formula for the performance of vortex whistles was proposed by its discoverer on the basis of tests; it is confirmed below on the basis of elementary physical considerations which show that high velocity and multi-dimensionality of the jet are essential.
“Exploring Tones”: Discredited by a Siren Experiment
Authors: Meyer Max F.
Published: September 2005

At least four times in the history of acoustics the assertion has appeared in print that the existence “somewhere” (in the air or in the middle ear or in neuro-chemistry) of a (not consciously heard) harmonic can be tested by the audibility of beats of an exploring tone. where an exploring tone is defined as a physical tone of nearly the same frequency as the frequency of the “hunted” tone. This assertion will be shown to be baseless and purely fictional.
Analysis of Hypex Horns
Authors: Ścibor-Marchocki Romuald I.
Published: September 2005

Impedance transformations of the “Hypex” horns are derived for all cases of mismatch for both increasing and decreasing characteristic impedance. A method of using a Smith Chart for these transformations is presented. The results are applicable to cases where losses are appreciable.
Two-Projector Null Method for Calibration of Hydrophones at Low Audio and Infrasonic Frequencies
Authors: Trott W. James , Lide Edward N.
Published: September 2005

Theory and procedure are presented on an absolute method for calibration of hydrophones in a closed water-filled tank. Unlike other absolute methods presently in use, it depends on a factor that is independent of frequency and is easily measured statically. This factor (0.1 Bl/area) plus voltage and current measurements yields the hydrophone free-field receiving response. The apparatus includes a displacement detecting circuit on one projector, and a means of changing phase and amplitude of the electrical current driving one projector relative to the current driving the second projector. The method has been used over the frequency range from 0.1 to 500 cps with an accuracy in response measurement better than ±12 db.
Effect of Damping and Vibration Detector Position in Resonance Measurements
Authors: Ryan John A.
Published: September 2005

Vibrations in a finite-length, thin rod at low frequencies are considered. Two cases are discussed. In the first, the pressure amplitude at the driven end is assumed constant and, in the other, the particle-velocity amplitude is taken as being constant.

An oscillatory character to the amplitudes of the resonance peaks is found which is a function of detector position and attenuation.

This phenomenon may explain the observed differences in the heights of the resonance peaks, and the recurrence of groups of large and smaller peaks in rods, plates, shells, and other vibrating systems. It may also have a considerable effect on the apparent Q (or bandwidth) of the resonance curves.
Phonon Viscosity and Its Effect on Acoustic Wave Attenuation and Dislocation Motion
Authors: Mason Warren P.
Published: September 2005

When dislocations move through a crystal, they are damped by some thermal mechanism. It is shown in this paper that good agreement with available measurements is obtained if the dislocations are damped by phonon viscosity. Phonons are quantized sound waves, which carry the thermal energy in an insulator. The interchange of energy between the longitudinal branch and the two shear branches occurs through the nonlinear elastic constants of the solid and requires a finite time τ. The effect of a shear wave, which is equivalent to a compression in one direction and an equal extension at right angles, is to raise the instantaneous temperatures for those phonons having components along the compressed direction and to lower the temperature for those having components along the extended direction. The flow of heat between the hot and cold phonons produces a damping of the sound wave corresponding to a viscosity η = E0K/CvV̄2 as long as the time of application of the shear wave is long compared to τ. When the product ωτ≫1 this source of loss disappears. Phonon viscosity contributes directly to the acoustic attenuation and indirectly produces a damping for dislocation motion.

By using thermal and sound velocity measurements to evaluate the viscosity, it is shown that available data on the attenuation of sound in metals and nonconducting crystals are in agreement with the calculated values of dislocation damping by phonon viscosity. A direct check for both edge and screw dislocations is obtained from recent work on the velocity of dislocations in lithium fluoride. The variation of internal friction in quartz as a function of temperature is in agreement with the temperature variation of phonon viscosity, but is not in agreement with calculations by Eshelby and Leibfried on dislocation damping by thermoelastic effects and by phonon scattering.
Structure and Velocity of the Periodic Vortex-Ring Flow Pattern of a Primary Pfeifenton (Pipe Tone) Jet
Authors: Anderson A. B. C.
Published: September 2005

Visualization of the vortex flow pattern in typical primary Pfeifenton jets was made by means of shadow-graph techniques to show the transition in form of the vortex pattern as it moves downstream in the jet, as well as, the dependence of the downstream translational vortex velocity and the geometry of the vortex pattern on the Reynolds number of the jet.

Results of experiment are compared with available theory. These studies were carried out with carbon dioxide jets discharging into the atmosphere. The flow channel geometry consisted of a pipe 78 in. in diameter, 12.013 in. long effectively, open at one end which was inserted into a large stilling tank and terminated at the other end by an orifice plate containing a sharp-edged circular orifice, 0.250 in. in diameter and 0.093 in. thick.
Interferometric Analysis of Even Harmonic Distortion of Ultrasonic Waves
Authors: Mayer Walter G.
Published: September 2005

Placing two transducers in an ultrasonic wave one-half wavelength apart in the direction of sound propagation and comparing the electrical signals from the transducers is used to record even harmonic components of a distorted ultrasonic wave while the fundamental and odd harmonics are canceled.
Acoustical Properties of Carpet
Authors: Harris Cyril M.
Published: September 2005

The acoustical properties of carpet are of interest in the design of auditoriums and studios, since the absorption which it contributes may be quite significant. However, little data exist on the acoustical properties of carpet and the scanty data available make no distinction among the various types of carpet. This paper describes measurements of the normal absorption coefficient and flow resistance for a wide variety of carpet samples. The normal absorption data were used to investigate which of many variables in carpet construction are important from the standpoint of acoustical absorption. On the basis of these data, certain key samples were selected for chamber test at the National Bureau of Standards for comparison with the tube measurements.
Directional Properties of Continuous Plane Radiators with Bizonal Amplitude Shading
Authors: Martin Gordon E. , Hickman John S.
Published: September 2005

The problem of reducing the levels of the minor lobes of linear, rectangular, and circular radiators is considered theoretically. The shading is accomplished by using equiphase normal-velocity distributions limited to two discrete amplitudes. Relationships are derived for the sound-intensity directivity pattern and the directivity index of each radiator. An exhaustive study of various directional properties of such radiators is undertaken. This information is presented in terms of the behavior of the major-lobe width, minor-lobe levels, and directivity index as functions of (1) the ratio of the two normal-velocity amplitudes and (2) the fraction of the unit having the higher source amplitude. It is shown that linear and rectangular radiators with such source distributions can be designed so that all minor-lobe levels are at least 21 decibels lower than the major-lobe level; the corresponding value for the circular radiator is 28 decibels. The resultant increase in major-lobe width is approximately twenty percent. The results are presented so as to provide criteria for the effective use of this method in transducer design.
Effects of Noise on Eosinophil Levels of Audiogenic-Seizure-Susceptible and Seizure-Resistant Mice
Authors: Anthony Adam
Published: September 2005

The occurrence of a diurnal rhythm in circulating eosinophils is described in mice selected on the basis of susceptibility to sound-induced audiogenic seizures. Daily exposures of seizure-susceptible and seizure-resistant mice to single, short noise bursts for 30 days does not abolish or alter this rhythm, provided a recovery period is allowed between the last stimulation and the time of blood sampling. A single noise stimulus is followed by a moderate eosinopenia seizure-resistant mice and a marked eosinopenia in seizure-susceptible mice in about 3 hours; recovery occurs in both cases within 24 hours. A prolonged eosinopenia occurs with several successive noise bursts—at a moderately low level (ca 250 eosinophils/cu mm blood) in seizure-resistant mice and at lower levels (ca 100 eosinophils/cu mm blood) in mice which experience convulsions during treatment. It was concluded that noise stimulation acts as a mild stress stimulus and is harmful only when it results in the production of fatal convulsions.