bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Relations between Normal Hearing for Pure Tones and for Speech
Authors: Jerger James , Carhart Raymond
Published: September 2005

The present American standards for normal hearing for audiometric purposes imply that the difference between audiometric reference zero for a 1000-cps pure tone and audiometric reference zero for spondee words is 6 db (i.e., approximately 16 db SPL for a 1000-cps tone and 22 db SPL for spondee words). An accumulation of evidence from several sources suggests, however, that the difference between the two thresholds is considerably larger than 6 db. The present study was designed to assess the effects of sex, ear, order of test presentation, method of threshold measurement, and degree of prior familiarity with spondee vocabulary on the difference between the threshold for a 1000-cps tone and the threshold for spondee words, as measured with W-1 recordings. Subjects were 126 young adult college students. Results indicate that the difference varies from 12 to 14 db, depending slightly on degree of prior familiarity with the spondee words, and on the method used to measure the pure tone threshold. The average speech threshold SPL in the present group agreed closely with the current standard reference level of 22 db, while the average 1000-cps pure tone threshold SPL was 6 to 8 db lower than the current standard reference level of 16 db. [This research was supported by the U. S. Air Force under Contract No. AF 41 (657)-185, monitored by the School of Aviation Medicine, USAF, Randolph Air Base, Texas.]
The Cocktail Party Revisited
Authors: Pollack Irwin
Published: September 2005

The employment of directional information of the desired talker in a multitalker environment has been termed the “cocktail party effect.” We have attempted to determine whether the addition of (1) “comb” filtering, which enhances the perception of spatiality [M. R. Schroeder, J. Acoust. Soc. Am. 29, 774 (1957)], or (2) splitting the speech frequency range, which enhances multichannel listening [W Spieth and J. Webster, J. Acoust. Soc. Am. 27, 866 (1953)] will improve the cocktail party effect, as previously defined [I. Pollack and J. M. Pickett, J. Acoust. Soc. Am. 29, 1262 (1957)]. The introduction of frequency separation does not remove the cocktail party effect. Intelligibility decreases as the frequency subdivision becomes more gross. However, it may be noted that a communication system based upon crude frequency separation and binaural listening may still be effective for certain instances of low-information communications. Specifically, PB monosyllabic word intelligibility of over 30% may be achieved with 4 background talkers in each of two split-frequency channels. This is equivalent to employing 11 transmitters, shared in pairs among 55 different talkers.
Sound Propagation in Flexible, Porous Media
Authors: Lang William. W.
Published: September 2005

A theory is developed for the propagation of plane, longitudinal waves through a material which is both flexible and porous. An idealized model is constructed consisting of an array of parallel elastic rods uniformly spaced in air. Viscous and inertial coupling forces, as well as pressure squeezing accompanying sidewise expansion of the rods, are responsible for interaction between the air and solid of the model. Two dilatational waves are found in the unbounded medium. The propagation constants describing these waves are written in terms of 6 dimensionless parameters characteristic of the model. Boundary conditions are introduced and an expression is obtained for the acoustic impedance at the front surface of a rigidly backed model of finite thickness. It is shown that viscous coupling forces are of predominant importance in controlling the amount of acoustic energy converted into heat at the internal surfaces of the material. Viscous coupling also determines the amount of energy transferred from the airborne sound waves to the interior of the solid where dissipation may take place if internal losses are appreciable. Preliminary data relating theory to experiment are presented.
Resonance Absorption: A New Absorption Mechanism in Solids
Authors: Liebermann Leonard
Published: September 2005

Thermal oscillations in molecular solids are of two distinct classes: lattice vibrations or the acoustical branch, and molecular vibrations or the optical branch. These two vibrational classes are weakly coupled; hence the exchange of energy is negligibly small except when these two branches overlap in frequency and “resonate.” This phenomenon is closely analogous to the exchange between two weakly coupled pendula; appreciable energy is transferred only at or near resonance, in which case the rate of transfer is slow. Stated in other terms, the relaxation time in resonant processes is usually lengthy. A long relaxation time is often manifested as anomalously high acoustic absorption. The relaxation time and hence the absorption in molecular solids can be calculated, using the procedures of a time-dependent perturbation calculation in quantum mechanics. Molecular constants for the calculation are obtained from the Lennard-Jones potential. Calculation shows that many molecular solids can be expected to exhibit unusually high acoustic absorption resulting from resonance absorption. As an example, benzene was studied experimentally. A single crystal of average linear dimension 10 cm was grown from the liquid. Absorption measurements using pulse techniques were made in the frequency range from 3 to 10 Mc. At 10 Mc the observed absorption has the excessively high value, 0.2 cm−1; this value is within limits of the theoretically predicted value. Thus resonance absorption in many molecular crystals can be expected to be 10 to 100 times greater than other absorption processes.
Debye Temperature of Vitreous Silica
Authors: Anderson O. L.
Published: September 2005

The vibrational spectrum of vitreous silica is of interest because the two methods of approximating the acoustic branch of the spectrum lead to conflicting values of the Debye temperature. Ultrasonic data lead to the value θD(elastic) = 1340° in contrast to specific heat data which lead to the reported value θD(thermal) = 130°. It is shown that infrared data are consistent with θD(elastic), but not θD(thermal). It is concluded that θD(elastic) is the more reasonable representation of acoustic vibrations indicating that the low-temperature specific heat arises from nonacoustic lattice vibrations. The low-frequency, nonacoustic vibrations of vitreous silica are conjectured to arise from the transverse modes of the oxygen ion. The unusual features of the vibrational spectra of vitreous silica appear to arise from the silica structure rather than the vitreous state.
Ultrasonic Relaxation in Methyl Cyclohexane
Authors: Piercy J. E.
Published: September 2005

Previous investigators have demonstrated the presence of an ultrasonic relaxation in cyclohexane derivatives and the fact that it is caused by the transition between two rotational isomers. With the aim of studying the nature of the isomers and the transition between them, the ultrasonic absorption of solutions of methyl cyclohexane and related molecules in organic solvents has been measured over a range of frequency, concentration, temperature, and solvents. The energy difference between the two chair forms of methyl cyclohexane was found to be approximately 2 kcal/mole in agreement with the model of Pitzer et al. The transition probability was found to depend only on a process internal to the molecule, rather than on intermolecular collision efficiency as in the relaxation of vibrational and rotational energy. The values of the kinetic parameters (frequency factor ∼ 1012 sec−1 and activation energy ∼ 10 kcal/mole) indicate that the path of transition between the two chair isomers is a direct inversion through the planar configuration, similar to the inversion of ammonia.
Second Choice Behavior in Intelligibility Tests
Authors: Clarke Frank R.
Published: September 2005

In a series of intelligibility tests, the listeners responded not only with their best estimate of which word had been sent on any given stimulus presentation, but also with their “second best” estimate of which word had been sent. These tests employed closed sets of items with the intelligibility of the items being depressed through the introduction of Gaussian noise into the communication circuit. Confusion matrices, showing the probability of each response given a particular stimulus, are presented for both first and second choice responses. The relationship between the entries in these pairs of matrices is discussed and rates of information transmission for first choice and second choice responses are compared. Also, a comparison is made between the rate of information transmission when two responses are made to each stimulus item and the rate when a single response is made to each item. [This research was supported by the U. S. Air Force under Contract No. AF 19(604)-1962.]
Word Frequency and Speech Intelligibility for Unknown and Known Message Sets
Authors: Decker Louis , Rubenstein Herbert , Pollack Irwin
Published: September 2005

The average frequency of occurrence of a word has been shown to be an important determinant of its intelligibility in noise; at least with naive observers listening to words drawn from an unknown set. On the other hand, with known message-sets, the discriminability or interconfusability among the items has been shown to be a prime determinant of intelligibility. Thus, with known message-sets, we might reasonably expect that word-frequency effects would be substantially reduced. We have carried out experimental tests which confirm this expectation. Defined message-sets, composed of eight monosyllabic words, were presented to a crew of five listeners at six speech-to-noise ratios under two conditions: (1) as an unknown message-set in which the specific words employed had to be discovered by the listener, and (2) as a known message-set in which the specific words employed were furnished to the listener before testing. Each defined set contained words representing a wide range of frequencies of occurrence. When the message-set was unknown, substantial word-frequency effects were observed—the speech-to-noise ratio at 50% intelligibility decreased about 2.1 db for each tenfold change in the average word frequency. When the message-set was known, no consistent word-frequency effects were observed.
Detection of Noise Signals in a Masking Noise
Authors: Green David M.
Published: September 2005

The detectability of several noise signals having different band widths and durations was determined. When the signal band width is equal to the band width of the masking noise the experimental procedure is identical to that which one would use to determine the observer's differential intensity sensitivity to noise. Two experiments were performed. In one experiment a noise burst with a 600 cps band width was used as a signal. The masking noise was wide band. The detectability of this narrow band signal is independent of the center frequency of the signal band. This result is consistent with a model which assumes the critical band may be increased in width to match the signal band width. The detectability of a wide band (500 cps) signal also bore out this assumption. In the second experiment the parameter signal duration was investigated. These results were consistent with a statistical decision model which predicts the results of both experiments. The equation, which expresses all the results with a reasonable degree of accuracy, asserts that to maintain some constant detectability (e.g., threshold) S0N0 = a1(ωT)12 where ω = signal band width, T = signal duration, S0 and N0 are the noise power per cycle of signal and noise, respectively, and a is an individual constant. (The first experiment was conducted at the Bell Telephone Laboratory. The second experiment was completed at the Electronic Defense Group with funds provided by the Operations Application Laboratory, Air Force Cambridge Research Center.)
Re-Evaluation of Weber's Law for Pure Tones
Authors: Tanner Wilson P.
Published: September 2005

The fact that Weber's law appears to apply in the same way both to intensity discrimination for pure tones and to intensity discrimination for white noise poses a theoretical paradox: in the case of pure tones, the human observer becomes less efficient as the intensity of the tone is increased, while in the case of white noise he exhibits a constant efficiency independent of intensity. At the May, 1957, meeting the author reported experiments conducted with pure tones in noise background suggesting that efficiency is constant rather than decreasing. New data show that with lower noise levels efficiency decreases although not as fast as Weber's law would suggest. The hypothesis that a random amplitude variation in the audio oscillator could lead to these results was tested and found tenable. Physical measurements are illustrated demonstrating the existence of noise of the required order of magnitude (50 db below the oscillator output). The argument is then extended to experiments done in “quiet.” Amplitude variation of oscillators, which is narrow band noise around the frequency of the signal, is sufficient to be consistent with the hypothesis that Weber's law for pure tones can be the result of a property of apparatus rather than a property of the hearing mechanism. (This work was carried out under sponsorship of Evans Signal Laboratory, Signal Corps Engineering Laboratories, Fort Monmouth, New Jersey.)
Reproduction and Identification of Elements of Auditory Displays
Authors: Johnson Lawrence , Pollack Irwin
Published: September 2005

Will the reproduction or the production of elements of auditory displays assist the listener in identifying the display? Apparently not, at least for relatively short training sessions. Listeners attempt to identify one of 12 tones spaced logarithmically over the frequency range of 932–1760 cps. After introduction of the extremes of the range of frequencies, four conditions of training were examined: (1) the observer was uninformed of the correctness of his response; (2) after each response, the observer was told the correct response; (3) in addition, a push-button oscillator was available for production of the tone; or (4) the observer attempted to produce the tone by whistling. During training, the methods of production and reproduction did, indeed, result in superior identification. However, in a following control test without information of the correctness of response, methods (2), (3), and (4) resulted in essentially equivalent performance. The results suggest that tying a distinctive motor response, as by production or reproduction, with a single variable of an auditory display will, as such, not result in substantial improvement of display identification.
Effect of Intensity Duration and Spectrum on the Perception of Two-Element Auditory Sequences
Authors: Sandel T. T. , Stevens K. N.
Published: September 2005

Recently, interest has been shown in the perception of acoustic stimuli embedded in a sequence of sounds, particularly in relation to studies of speech perception. The particular question we have asked is: How is the perception of a given sound influenced by the physical parameters of a sound adjacent to it in temporal sequence? In the present experiments each stimulus comprises two components separated by a 10 msec gap; each component is a noise of specified band width, center frequency, intensity, and duration. Two of these stimuli are chosen as standards in a given experiment, and listeners are required to place other stimuli into one of the two categories typified by the standard stimuli. In a typical experiment, each of the standard stimuli consisted of two components that were equal in all respects except duration. After hearing these standards, subjects were required to categorize each of a series of ambiguous stimuli in which relative duration and intensity were manipulated. Results demonstrated a trading between intensity and duration, although the relations did not follow a simple pattern. In other experiments using different pairs of stimuli as standards, we have studied the influence of noise center frequency and band width as experimental variables. [This work was supported in part by the U. S. Army (Signal Corps), the U. S. Air Force (Office of Scientific Research, Air Research and Development Command), and the U. S. Navy (Office of Naval Research); and in part by the National Science Foundation.]
System for the Measurement of Noise Exposure
Authors: Cox Jerome R.
Published: September 2005

To evaluate the noise exposure on the flight deck of aircraft carrier, a system has been developed that gives a statistical description of the noise experienced by personnel involved in the launching of jet aircraft. The system utilizes a small portable FM transmitter that can be easily carried about the flight deck to monitor an individual's noise exposure. The signal received from this transmitter is recorded on magnetic tape and, at a later time, analyzed by means of a device called the “Cumulator.” The Cumulator measures the total time that the intensity level of the noise exceeds each of seven preset levels. The Cumulator has three separate channels, each capable of analyzing a different position of the frequency spectrum. Typical cumulative distributions of the noise exposure for flight-deck personnel will be presented.
On the Behavior of Ear Protection Devices below 1000 cps
Authors: Witchey A. L.
Published: September 2005

An extensive set of measurements has been made on various type of ear protection devices, generally consisting of a hard-shelled volume coupled to the head by an annular pad filled with various materials. Attenuation measurements were made with a miniature pressure microphone. Accelerometers were used to measure the motion of the shells and head. Attenuations as high as 40 db at 20 cps have been obtained using volumes of the order of 2000 cc coupled to the head with a liquid-filled pad. (This work has been supported by Contract AF 33(600)-33172.)
A High-Intensity Sound Reverberation Chamber and Loudspeaker Noise Generator
Authors: Fiala W. T. , Hilliard J. K.
Published: September 2005

This paper will describe a high-intensity sound test chamber capable of producing 150 db and having a working area of 6 × 3 × 112 ft. The chamber uses the principle of reverberant sound to test electronic packages used in aircraft and missiles. Double wall construction and use of Aquaplas for panel damping provide the necessary sound insulation. Complete instrumentation and the loudspeaker generator will be described.
Sound Radiation from High Reynolds Number Turbulence
Authors: Kraichnan Robert H.
Published: September 2005

It has been found, on the basis of a recent, anticipatedly exact theory of homogeneous turbulence, that the acoustic power radiated at high Reynolds numbers and low Mach numbers is dominated by the high-frequency contributions from the inertial wave-number range. The inertial range pressure wave-number spectrum in the isotropic case has been found to be P(k) = aρ2εv0k−2, where ρ is density, ε is the dissipation rate by viscosity, per unit mass, and v0 is the rms turbulent velocity in any direction. The universal number a is determined by the theory. The power spectrum of the inertial range radiation per unit mass has been found to be W(ω) = AM5εω−1, where M is the Mach number v0/c and the universal number A is determined by the theory. The total inertial range radiation power is of order AM5εlnR02/3, where R0 is the Reynolds number v04/εν (ν = kinematic viscosity) which characterizes the turbulent macrostructure. In the present paper, an attempt will be made to give an elementary physical interpretation of these results in terms of the dynamical interaction of the sharply defined shear fronts and vortex filaments which make up high Reynolds number turbulence. Some implications for radiation from jets, wakes, and boundary layers will be discussed briefly. (The research described was supported by the Mechanics Branch, Office of Naval Research.)
Self-Maintained Transverse Oscillations of a Jet
Authors: Nyborg Wesley L.
Published: September 2005

A thin flat (subsonic) jet, temporarily divided by an edge, tends to set itself into transverse oscillation; the accompanying sounds have been called “edge tones.” Any of a number of modes or “stages” may be excited, depending on parameters of the system and on its history. When a resonator is present (as in an organ pipe) further complications appear. Although acoustical and hydrodynamical characteristics of the apparently simple jet-edge system have been studied for over a century, complete theory still does not exist. An adequate theory should account for the frequency characteristics, jet oscillalation configurations, and self-maintenance conditions for the different modes, as well as for the generated vortex arrays. In this paper available information on characteristics of jet-edge and jet-edge-resonator systems will be reviewed, and the more recent theoretical approaches discussed.
Aeolian Tones
Authors: Etkin B.
Published: September 2005

This paper gives an account of current research on aeolian tones at the Institute of Aerophysics, University of Toronto. Previous work (reported at I.C.A. Congress, June 1956) is being extended by (1) measurements of the surface pressures, and their correlations along the cylinder and (2) measurements of the force amplitudes. A comparison is made of the measured sound intensity with that predicted by the theory.
New Developments in Ultrasonic Dentistry
Authors: Tascher Paul J.
Published: September 2005

The contribution of acoustics to dentistry originates from the industrial application of drilling hard materials. The ultrasonic technique of cutting teeth has been established. A new ultrasonic generator to operate interchangeable magnetostrictive transducer inserts was designed for the specific needs of dentistry. Among the uses of this apparatus are: cleaning of teeth, treatment of diseased gingival, condensation of amalgam fillings and chemical immunization, and desensitization of teeth. The instruments designed for cleaning teeth and treatment of gingival disease are described. Dental calculus and stains are removed effortlessly and with little trauma to dental structures. The cavitational effects to degas and disperse therapeutic chemical are applied in the treatment of gingival disease. Tissues heal rapidly by treatment with dilute sodium hypochlorite. Insert transducers were designed for the condensation of amalgam filling material. Research established that ultrasonic condensation increased the compressive strength. A technique for this purpose is established. The use of chemicals with ultrasonics for the desensitization and immunization of teeth against decay is being investigated. Fluorides may be ionized and dispersed by cavitation to penetrate tooth structure.
Novel Ultrasonic Hand Instrument
Authors: Kleesattel Claus , Balamuth Lewis
Published: September 2005

A new hand instrument, having numerous ultrasonic uses, and operated in the 25 kc/sec range, will be described and shown. This device is entirely portable and features a light weight hand-piece, which permits quick change of the transducer insert elements, without conventional mechanical attachments. The small electronic generator is of a new type and is semi-automatic insofar as frequency selection and control are concerned. The operating characteristics of this instrument will be described. Special emphasis will be given to the vibratory properties of the transducer which is utilized to produce simultaneously controlled longitudinal and flexural vibrations. This results in a variety of motions at the instrument's operating end. Practical design considerations led also to a new transmission line for connecting the magnetostrictive transducer to the operative output elements. An elementary coupling theory for the flexual and longitudinal vibrations will be presented in order to account for the elliptical mechanical motions achieved in practice.
Investigation on the Ultrasonic Agglomeration of Fine Material in Water
Authors: Carlin Benson
Published: September 2005

An investigation has been carried out in connection with fine material of the order of a few microns suspended in water. It was desired to treat approximately 1 200 000 gal per day and to substitute ultrasonic methods for poacher house pits. A bibliography and study of work done to date indicate that no systematic study has been made in this field. Tests were made at cavitation and below-cavitation levels at several different frequencies ranging from 20 kc to 1 Mc. Breakdown of the fine material into small uniform particles was observed at cavitation levels and agglomeration at levels under those necessary for cavitation. All tests were made on laboratory samples. Every test was repeated a number of times to determine reliability. Results indicate that the method has promise for accomplishing the results desired. [The work was sponsored by Hercules Powder Company and the Radford Arsenal.]
Concert Hall Design
Authors: Beranek Leo L.
Published: September 2005

A detailed study of 27 concert halls of Austria, Canada, Denmark, England, Finland, Germany, Holland, Israel, Scotland, Sweden, Switzerland, and the United States is presented. The results point to new procedures to be followed in design and explain many inconsistencies existing in the literature dating from 1900. In particular, the reasons why identical reverberation times at 500 to 1000 cps can occur in occupied halls with volumes per seat ranging from 180 to 350 ft8 are explained. The relative advantages and disadvantages of rectangular, fan-shaped, horse-shoe, and diamond-shaped plans are discussed. Comments on the general acceptance of particular halls by orchestras, audiences, and music critics in relation to the measurable acoustic parameters are made.
Reverberation Formula Which Seems To Be More Accurate with Nonuniform Distribution of Absorption
Authors: Fitzroy Dariel
Published: September 2005

Reverberation measurements, made in rooms where the absorption is nonuniformly distributed, usually vary widely from the predictions based on the usually employed formulas. Based on extensive tests made in a large number of rooms, where distribution of sound absorption varies widely in uniformity, an empirically derived formula is submitted, together with photographs of graphic recorder decay curves which seem to confirm the validity of the formula. The data submitted are a small portion of the accumulated measurements, covering a period of some five to six years, in rooms of widely varying volume, widely varying boundary ratios, and marked dissimilarity in amounts of absorption and ratios of absorption distribution.
Some Aspects of Boundary Layer Induced Noise
Authors: Powell Alan
Published: September 2005

A discussion on noise caused by the excitation of panels by turbulent boundary layers, commenting upon approaches based on infinite and finite walls, and illustrating the role of cross-correlation of the pressures at the surface.
Response of Plates and Membranes to Pressure Fluctuations of a Turbulent Boundary Layer
Authors: Strasberg M.
Published: September 2005

Calculations have been made of the flexural vibrations of a flat plate or a stretched membrane excited by pressure fluctuations in the turbulent boundary layer of a fluid flowing on one side of the vibrating surface, utilizing the data on the pressure fluctuations recently obtained by M. Harrison [J. Acoust. Soc. Am. 29, 1252(A) (1957)]. The spectral density of the amplitude of flexural vibration is calculated in terms of measured values of the spectral density of the pressure fluctuations and values of the two-point cross spectral density versus separation of the two points, using a theoretical relation similar to that of A. Powell [Douglas Aircraft Company report SM-22795 (May, 1957)]. The sound pressure resulting from the vibration is also calculated for points either very close or very far from the vibrating surface.
Estimate of the Generation of Fluctuating Surface Pressures on Hypersonic Vehicles
Authors: Callaghan Edmund E.
Published: September 2005

The fluctuating surface-pressure coefficient, i.e., the ratio of root-mean-square pressure at the surface to local dynamic pressure outside the boundary layer, has been shown to be approximately equal to the usual skin friction coefficient. Extremely large fluctuating pressures will be encountered on many missiles and manned aircraft by virtue of the extremely large dynamic pressures associated with high velocities. The integrity of electronic and associated gear may well be jeopardized by such high levels. This paper provides a means of estimating the probable minimum fluctuating surface pressures which will be experienced and indicates the nature of the frequencies which would be expected by virtue of high forward velocity.
Noise Characteristics of Helicopter Rotors at Tip Speeds up to 900 ft/sec
Authors: Hubbard H. H.
Published: September 2005

Evidence is presented which suggests that the noise of full-scale helicopter rotors results mainly from conditions of unsteady flow. Measured noise levels and spectra are presented for test conditions where gear train, engine, and other propulsion system noises are minimized. These data cover a range of tip speeds from 100 ft/sec to 900 ft/sec for various rotor disk loadings. Results indicate that both tip speed and disk loading have an important influence on the noise radiated from the rotor. During stall the noise levels increased at all frequencies, but particularly at the high end of the spectrum. As a matter of special interest, a highly peaked wave form caused by possible doppler effects was noted to be associated with high tip speed operation.
Segment Inventory for Speech Synthesis
Authors: Wang William S-Y. , Peterson Gordon E.
Published: September 2005

The inventory of segments required to synthesize normal American speech from recorded utterances has been partially investigated. A total of 43 phonetic units has been found essential, including a unit of silence. These units represent the segmental phonemes and some of the major allophones of these phonemes of the midwestern dialect of American speech. To obtain the segments, utterances are constructed involving the two desired phones with the proper intonation and stress environment. The utterances are recorded on magnetic tape, and the desired boundaries of the segments are determined by means of a technique including a sound spectrograph. An attempt is made to match harmonics, formants, and amplitude envelopes between adjacent segments. To synthesize the mid-western dialect of American speech it is estimated that an inventory of about 8000 segments is required. A sentence synthesized from approximately 47 such segments will be demonstrated.
Measurement of the Cross-Sectional Areas of Vocal Tracts
Authors: Wendahl Ronald W.
Published: September 2005

This work was done as part of a Ph.D. dissertation. Techniques (including lateral and laminagraphic x-ray photography, dental casts, palatograms and still photographs) were developed for estimating the cross-sectional areas of the vocal tracts of 6 subjects, 3 male and 3 female, who had been preselected to present wide variations in vocal cavity dimensions. The data for cross-sectional measures taken from the glottis to the lips of each of the subjects phonating each of five vowels were sent to the Acoustics Lab at Massachusetts Institute of Technology where appropriate adjustments were made on the vocal tract analog to approximate electrically the measured areas. Comparisons were made between the vowel formant frequency regions produced by the subjects and the formant frequency regions produced by the V.T.A. when adjusted to approximate subjects vowels. These comparisons provided indirect empirical validation of the measuring techniques.
Analysis of a Logarithmic Solion Pressure Detector
Authors: Wittenborn A. F.
Published: September 2005

A theoretical analysis is given of a solion pressure detector which has a direct current output proportional to the logarithm of the acoustic pressure input. An approximate method is used which avoids the necessity for solving the Navier-Stokes equation describing the fluid flow and the convection diffusion equation for calculating the current. The calculation consists of (1) solving the zero flow “transient” diffusion equation for the reducible component in the electrochemical redox system, (2) using this transient solution to calculate the output current with the time spent inside the detector orifice as the independent variable, and (3) relating this time to the pressure by using the known acoustic impedance of the detector orifice. The calculated results show that the logarithmic response is obtained through a combination of diffusion and hydrodynamic effects. For the ideal case of piston flow, the logarithmic response is degraded.
End-Fire Line Projector
Authors: Miller H. B.
Published: September 2005

The acoustic analogy of the endfire radio antenna sounds simple. But in practice the body or “baffle” supporting the acoustic array tends to destroy the endfire patterns. Some designs are discussed wherein the baffle is converted from a necessary evil to a thing of advantage. The array consists of resonant projectors.
Attenuation in Water-Saturated Marine Sediments between 20 kcps and 40 kcps
Authors: Shumway George
Published: September 2005

Sediment samples were placed in thin-walled cylindrical containers 2 in. in diameter and 5 in. long; these were driven as complaint-walled resonators at their lowest resonant modes. From measures of resonant frequency and mechanical Q, sound speed and attenuation were determined. A variety of natural sea-floor sediments, ranging from deep-sea clays to coarse sands from shallow water, have been studied. Lowest attenuations, 1 db/ft or less, were found in deep-sea clays and fine silts where porosity was greater than 0.75. Sediments of intermediate porosity, 0.75 to 0.45, had attenuations between 1 and about 7 db/ft. Sediments of porosity less than 0.45, which are sands, had attenuations between 2.5 and 4.5 db/ft. On a number of samples more than one resonant mode was obtained, and from these data there is an indication that attenuation increases as the first power of the frequency.
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 sound in the frequency region 50 to 100 kc 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. It is hoped that this knowledge will lead to an understanding of the fundamental mechanism of scattering at the air-water boundary. These measurements of reverberation, combined with observations. of several oceanographic and meteorological parameters, are presented. An examination of these data allows the following conclusions: (1) reverberation cannot be directly related to the wave height but is closely correlated with wind speed, (2) reverberation increases with wind speed to a wind of about 14 knots, but remains constant for higher wind speeds, and (3) 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. (This work was supported by the Bureau of Ordnance, U. S. Navy, under Contract NOrd 12937.)
Stroboscopic Vibration Analyzer
Authors: Edelman Seymour , Brooks R. R. , Smith E. R. , Kohrn S. , Jones E.
Published: September 2005

This paper describes a new instrument called a strobolyzer which makes it possible to observe, in slow motion, the vibrations of any body at any audio-frequency even though the amplitude of motion is microscopic. It can be used to determine resonant modes of complicated bodies or to observe changes in motion as changes are made in frequency, loading, or driving point. The motion to be studied is detected by a number of vibration pickups placed to show the interesting features of the motion. The signal from each pickup is at the vibrating frequency but, in general, will differ from the other pickup signals in amplitude and phase. In the strobolyzer, the signal from each pickup is mixed with a common signal which differs by a small amount, Δcps, from the vibrating frequency. The signals from the mixer, after filtering, are at Δcps and the amplitude and phase relations which exist among the signals from the pickups are preserved in the signals from the mixers. The signal from each mixer drives an indicator which is mounted on a rough model of the vibrating body in a position which corresponds to the respective pickup.
Techniques for the Measurement of High Intensity Sound
Authors: Dranetz A. I. , Oglacchio A. W.
Published: September 2005

This paper describes three types of high-intensity piezoelectric microphones, along with techniques of dynamic calibration covering temperature ranges from −65°F to +450°F. These microphones are useful for measurements up to −175 db. (1) A spherical type of microphone with some special emphasis on the omnidirectional characteristics will be described. (2) A compression type—the characteristics of a compression type flush diaphragm gauge will be presented. (3) A bender type—a novel approach on a bender type of microphone will be presented which should substantially lower the vibration characteristics. Over-all characteristics of temperature, frequency response, resonant frequency, and sensitivity will be discussed. Special emphasis will be placed on vibration sensitivity of these different microphones. In calibration the units are evaluated by three independent methods: one, a siren type of calibrator; second, a bursting diaphragm chamber; and third, a quasi-static type of dead weight test. (a) Siren type—the siren type calibrator has a frequency response from 10 cps to 2000 cps, and higher if necessary, and can handle dynamic calibrations up to 20 psi. (b) The punctured diaphragm type of calibration produces a pulse of 10-20 milliseconds with pressures up to 25 psi available. (c) The third calibration used is the well-known sound chamber comparison method. Curves and technical data will be presented to show correlation among these three systems, along with some design criteria on the microphones.
Method for Determining the Stability, Damping, and Venting Properties of Condenser Microphones
Authors: Hlasnik John J.
Published: September 2005

The stability, damping, and venting properties of condenser microphones were determined by subjecting the microphone diaphragm to pressure pulses up to 10 psi. This was achieved by enclosing the microphone in a chamber and evacuating it to controlled ambient pressure differentials. The microphone diaphragm was then shocked by exposure to ambient pressure pulses. The stability of the microphone was determined by calibrations made before and after pressure application. Damping and venting characteristics were determined by measuring the microphone rise and decay response due to the pressure pulse. Both damped and stretched diaphragm were investigated.
Stability of Bruel and Kjaer Condenser Microphones
Authors: Embleton T. F. W. , Dagg I. R.
Published: September 2005

The absolute sensitivities of a number of Bruel and Kjaer condenser microphones were measured using reciprocity techniques. All readings were corrected for the linearity and gain of the apparatus which existed at the moment of measurement. By taking six different pairs of readings instead of the minimum number of three which the reciprocity technique requires each calibration was checked for self-consistency and any erroneous reading detected immediately. The estimated absolute accuracy of the microphone sensitivities is ±0.08 db and changes in sensitivity may be measured to ±0.03 db: all measurements have been made at 400 cps. The temperature coefficient of sensitivity varied considerably from one microphone to another—from zero to as much as −0.015 db/°F. Some microphones showed a steady drift of sensitivity with time, in the worst case as much as 0.25 db in 6 months, while others showed no measurable change over longer periods. In all cases it was found that the microphone sensitivities were a function of the ambient pressure; the air cavity between the diaphragm and the fixed plate of the condenser contributes between 35 and 60% of the total stiffness of the diaphragm. The microphones are sensitive to shock, and irreversible changes in sensitivity of up to 1.5 db have been found for violent treatment.
Capacitance-Type Displacement Gauge
Authors: Shattuck Russell D.
Published: September 2005

A noncontacting displacement gauge is described which is linear throughout the audio-frequency range over a wide displacement amplitude range. The instrument employs commercially available condenser microphone circuitry to measure the displacement of any conducting surface. Entirely conventional audio-instrumentation may be employed to analyze test data obtained with the probe. A typical output voltage, with the gauge located 0.1 in. from the vibrating member, is 30 mv for a 0.001-in. displacement amplitude. The sensitivity in volts per inch of displacement is given approximately by S = 0.5/δ2, where δ is the static spacing between the probe and the vibrating plate. A simple accessory is described for checking the instrumentation sensitivity.
New Headset-Microphone for Military Use
Authors: Touger M. L.
Published: September 2005

The H-157(XA)/AIC is a new headset-microphone developed for the Air Force under contract AF 33(600)33172. In comparison with the II-78B/AIC now in general use, the H-157 has the following improvements: (1) weight is reduced 39%; (2) comfortable wearing time is in excess of 8 hr, an improvement of over 100%; (3) the noise attenuation is increased 10 to 15 db; and (4) the noise-to-noise PB word articulation score in 120 db jet noise is 71%, an increase of 20 points. In addition the headset has a substantially flat real-ear response, resulting in greatly improved speech quality. The H-157 employs a circumaural hard-shelled ear cushion with a foam- or liquid-filled sealing pad. The earphone used is the H-143/AIC, which weighs 35 g, has a 1000-cps sensitivity of 105 db/mw on a 6-cc coupler, and a substantially uniform coupler response to 5000 cps. With one watt power available and 10 db peak clipping, the headset will give an estimated 66% word articulation with the talker in quiet and the listener in 140 db of jet noise. The signal level at the ear is 115 db. The microphone, M-87(XA)/AIC, is much smaller and lighter than its predecessor, the M-33, and is lower in sensitivity. The sensitivity is adequate for use with the AN/AIC-10 and related systems.
Theory of Temporal Auditory Integration
Authors: Zwislocki J.
Published: September 2005

A series of experiments indicate that the ear is capable of integrating sound energy spread over 100 msec or so. This may be a valuable attribute of hearing, and its existence can probably be explained by some evolutionary processes. Nevertheless, it remains puzzling how a system that seems to simply count the sound waves, and to respond to sound pressure rather than to sound intensity, functions as a power integrator. The theory shows a possible solution. It is based on neurophysiological as well as on psychophysical observations. It agrees quantitatively with measurements of the threshold of audibility as a function of stimulus duration and it helps explaining the shape of the threshold curve at low and medium frequencies. It also indicates that the apparent approximate power integration is caused by specific neurophysiological time constants.
Continuous Recordings of Endolymphatic Oxygen Tension, Action Potential, and Microphonics
Authors: Misrahy George , Shinabarger Edward , DeJonge Bud , Arnold James
Published: September 2005

Endolymphatic oxygen tension, action potential, and microphonics were recorded simultaneously and continuously from the first turn of the cochlea of guinea pigs during and following acute asphyxia, loud sounds, and chronic hypoxia. The curves thus obtained will be compared. Endolymphatic hypoxia of the order of that induced by a loud sound produces marked changes in action potential and microphonics. These results will be discussed in terms of hypoxia playing an important role in the temporary hearing loss induced by loud sounds.
Effect of Intracochlear Injections of Glucose-Glucose Oxidose on the dc Potential, Microphonics, and Action Potential of the Cochlea of Guinea Pigs
Authors: Misrahy George , DeJonge Bud , Shinabarger Edward
Published: September 2005

In order to render the region of the basilar membrane hypoxic without affecting oxygen tension in the stria vascularis, a solution of glucose-glucose oxidase and catalase was injected in the various scalae. Whereas injections of deactivated solution and gluconic acid had essentially no effect, the active-glucose oxidase solution selectively depressed the action potential and microphonics with comparatively little or no effect on the dc potential. Injections of the active solution into SM1 abolished the action potential in response to a tone pip of 12 000 cps but not to a tone pip of 1 000 cps. Recordings from the round window of microphonics with a unipolar electrode did not reflect changes in microphonics occurring in either the second or third turns as a result of injections into SM2 or SM3 but they did reflect accurately changes in the first turn. Implications of these results will be discussed.
Sound, Vorticity, Entropy
Authors: Kovasznay Leslie S. G.
Published: September 2005

Up to recent times acoustics was primarily concerned with small amplitude irrotational motion of a compressible medium and fluid mechanics dealt with incompressible flow, consequently there was no overlapping area between those two disciplines. Presently, however, the importance of understanding both compressible flow and large amplitude waves in the presence of important viscous and heat conduction effects created a real need for a single unified discipline that includes both small amplitude irrotation waves and incompressible flow as special limiting cases. The full Navier-Stokes equations of a viscous heat conductive gas are strongly nonlinear. For weak fields, however, the solutions reduce to three independent “modes” and those can be identified as vorticity, sound waves, and entropy spots. A second-order theory indicates interaction between all the modes and the familiar examples such as sound generation by vorticity, sound scattering on entropy nonuniformities, heat convection by turbulence, etc., can all be accounted for by a single unified theory.
Shock Excitation of Powdered Solids. I. Spectroscopic Observations
Authors: Parkinson W. H. , Nicholls R. W. , Watson M. D.
Published: September 2005

Spectroscopic observations have been made in emission and absorption upon the luminosity which arises from the interaction between helium driven shock waves in argon and powdered solids. Astrophysically important metallic oxides, powdered meteorites, pure metals, and certain organic compounds have been subjected to shock excitation. The spectrum of the resulting luminosity is entirely molecular at low Mach numbers (4), entirely atomic at high Mach numbers (8), and mixed atomic and molecular at medium Mach numbers. Thus the shock tube appears to be an important new tool in the spectroscopic laboratory for the controlled excitation of spectra which are difficult to excite by more conventional means. Preliminary experiments which have been made using time resolved emission and time resolved absorption techniques have shown that the reflected shock wave is largely responsible for the excitation. The absorption experiments are also being performed to measure the oscillator strengths of bands of the metallic oxides.