bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Hydrodynamic Pressure Field near a Ship Propeller
Authors: Breslin J. P.
Published: September 2005

The increasing importance of propeller-excited vibration has stimulated interest in the study of the time-dependent pressure field in the neighborhood of a propeller in an incompressible fluid. It is demonstrated that an approximation of this field can be computed from a vortex representation and also that the result may be quickly obtained from the existing formulas for the sound-pressure field of a propeller as a limit for “zero” Mach number. The blade-frequency pressure for the simplest type of loading has been found to be expressible in terms of tabulated elliptic integrals. Evaluations in the case of a three-bladed propeller are compared with measurements made in water at the David Taylor Model Basin. The character of the dependence of the blade-frequency pressure with tip clearance and other parameters is well predicted by the theory but the magnitudes are seriously underestimated. (This work is the result of a study sponsored by the Bureau of Ships Fundamental Hydromechanics Research Program, administered by the Taylor Model Basin under Contract Nonr 263-16.)
Fundamental Problems in Speech Physiology
Authors: Peterson Gordon E.
Published: September 2005

From the information theory viewpoint, the combined neural and motor mechanisms of speech production serve as the primary information source in oral communication. While extensive studies of motor mechanisms in human physiology have been made during the past decade, there has been little advance in understanding the physiological processes of speech and in the development of instrumental techniques for the study of the physiology of speech. There is at present much opportunity for the development of basic physical theory of speech sound formation and for experimental research with modern electro-acoustical instrumentation on speech generation. The research opportunities apply to all aspects of speech production, including respiration, phonation, articulation, and nasalization. In such studies, fundamental consideration must be given to the interactions of the mechanical and the acoustical aspects of speech sound production.
Sinusoidal Pressure Generator with Wide Amplitude and Frequency Ranges
Authors: Perls T. A. , Miles D. O.
Published: September 2005

The sinusoidal pressure generator (SPG) produces pressure changes suitable for fundamental studies of liquids and also for calibration of pressure gauges. The present model yields pressure up to ten atmospheres at any frequency from zero to well over 10 000 cps. The pressures are proportional to the excitation voltage within ±5% from zero to 10 000 cps. The SPG consists of a piezoelectric driver (24 disks of a BaTiO3 ceramic), a fluid cavity and provisions for mounting test devices. All components are contained in a heavy-walled brass cylinder 4.0 in. in diameter and 3.2 in. high. The peak displacement obtainable without undue heating of the BaTiO3 is approximately 10−5 cm. The fluid cavity is approximately 1.25 in. in diameter and 0.040 in. deep and is sealed by a thin Mylar membrane. The monitor crystal is a BaTiO3 cylinder, 116 in. o.d. and 116 in. high (output sensitivity approximately 40 mv per atmosphere). The cavity forms one end of an interchangeable plug which accommodates pressure gauges having diameters up to about one inch. This plug can also be provided with a thick diaphragm, directly behind the fluid cavity, for deflection measurements by means of a very sensitive capacitance-type device, the Resonant Bridge Carrier System. Typical calibrations of commercial pressure gauges will be shown.
New, Lightweight, Earphone and Microphone for Military Use
Authors: Rogers F. K. , Farr C. E. , Carrell R. M.
Published: September 2005

The H-143 is a new earphone for military use. Its weight is 35 g; its sensitivity, 105 db/mw in a 6-cc coupler. In a 40-cc foam cushion (the MX-2088), it has an essentially flat real-ear response with a cutoff frequency of 5000 cps. The H-143 is altitude-compensated with a minimum sensitivity of 100 db/mw at 25 000 ft altitudes. The acoustical and mechanical design which contributes to this performance is discussed. The H-143 was developed under contract AF 33(600)-22924 and is a component of the H-157(XA)/AIC headset-microphone. The M-87(XA)/AIC is a new, boom-mounted, noise canceling microphone for military use. It belongs to the family of microphones for the Air Force AN/AIC-10 intercommunication set. It is one-half the weight of the M-33 and has a sensitivity equal to the M-55/AIC. The M-87 can be installed in oxygen helmets. The mechanical and acoustical design of the microphone is discussed. It was developed under Air Force Contract AF 33(600)-33172 as a component of headset-microphone H-157(XA)/AIC.
Audio Spectrum Analyzer Employing Gaussian Filters
Authors: Harris Cyril M. , Klapper Jacob
Published: September 2005

This paper describes a 54-channel audio spectrum analyzer. Each channel has a transmission characteristics which very closely approximates the shape of a Gaussian probability curve, The advantages of such filters will be discussed.
Theory of Periodic Shocks and Large Amplitude Gas Oscillations in a Closed Tube
Authors: Saenger Alfred , Hudson George E.
Published: September 2005

When a piston oscillating with a finite amplitude at one end of a closed tube drives the enclosed gas at a frequency near a natural acoustic frequency of the system, the pressure observed at various positions along the tube shows the presence of a shock wave moving periodically back and forth [G. E. Hudson and A. Saenger, Phys. Rev. 99, 633(A) (1955); G. E. Hudson, J. Acoust. Soc. Am. 28, 154(A) (1956)]. A theory of the gas motion has been developed which includes effects of wall friction and heat exchange, and allows for the presence of shocks. The theory includes a condition in the form of a relation between the driving frequency of the piston motion and its amplitude which specifies when shocks should first appear. An approximate solution of the equations of motion and shock conditions at resonance represents the motion as the sum of a forced continuous motion and a free discontinuous one. Conditions of periodicity and single valuedness applied to this solution and considerations of energy transfer through the system lead to expressions for the shock amplitude, the relative phase of shock and piston motions, and the average temperature of the gas in terms of the amplitude of the piston motion. (Supported in part by the Technical Research Group, New York, New York.)
Shock Excitation of Powdered Solids. II. Physical and Chemical Changes upon the Powder Grain Surfaces
Authors: Nicholls R. W. , Parkinson W. H. , Watson M. D.
Published: September 2005

In an attempt to understand some of the physical processes involved in the interaction between helium driven shock waves in argon and powdered solids, microscopic, x-ray, and chemical techniques have been employed in conjunction with the spectroscopic observations to study the changes in grain surfaces before and after shock treatment. The shock wave particle interaction has many points of similarity to that of the traversal of a meteoroid through the upper atmosphere and, as expected, evidence of severe surface ablation has been noted in many cases. In some, interesting surface chemical changes have occurred (e.g., Fe2O3 → Fe3O4) and in others [AgCN, Fe3Co(CN)6] the formation of carbon, as soot particles, has been correlated with the spectra.
On the Dynamics of a Bull Whip
Authors: Bernstein Barry , Hall Donald A. , Trent Horace M.
Published: September 2005

It appears that this well-known device has never been discussed in the literature. The popular notion of how it produces such a loud report is that leather is made to hit upon leather. It is shown as a matter of fact that the sharp crack of the whip arises when its tip exceeds the velocity of sound, thus generating a shock wave. The motions executed by this device together with the speed multiplication produced make it an interesting mechanical contrivance
Results of Field Measurements on Some Runup Noise Suppressors
Authors: Pietrasanta A. C. , Doelling Norman
Published: September 2005

Detailed acoustical measurements have been conducted on several types of runup noise suppressors, including: (1) a coupled exhaust unit, (2) separately coupled intake and exhaust units, (3) a complete enclosure, and (4) a runup pen. In most instances, the measurement procedure consisted of recording sound pressure levels as a function of octave bands of frequency both on a close-in rectangle and on a 250-ft semicircle about the aircraft, with and without the suppressor in place. The results of these measurements will be compared, particularly to point out the noise reduction characteristics as a function of both angle and frequency for each type of suppressor. In addition to noise reduction per se, the suppressor designer is also interested in how his design may be improved. Toward this end analyses have been performed to determine the relative contributions of the various “noise sources” of an aircraft-suppressor combination (suppressor exhaust opening, primary air inlet opening, secondary air inlet opening, etc.) to the noise levels at 250 ft. An example of such an analysis is described, and calculated, and measured sound pressure levels at 250 ft are compared. [Supported in part by the U. S. Air Force under Contract Nos. AF 33(616)-2151, AF 33(616)-3335, and AF 33(616)-3938.]
Mechanical Impedance of the Forehead and Mastoid
Authors: Smith Ernest L. , Corliss Edith L. R. , Eanet June
Published: September 2005

Further measurements of the resistive and reactive components of the mechanical impedance of the human forehead and mastoid have been made on a group of normal subjects between the ages of 18 and 25 years. The driving system consisted of a cylinder of polarized barium titanate mounted on the 200-lb mass of a pendulum supported by an A frame. Force and displacement were measured close to the point of contact with the load. The impedances determined in this study for a 2-cm driving tip are similar to the results of a pilot study by Corliss and Koidan [J. Acoust. Soc. Am. 27, 1164 (1955)], in which they reported that the predominant characteristic of both forehead and mastoid is a stiffness reactance with some damping over most of the audio-frequency range.
Investigation of Monaural Interaction of Closely Spaced Clicks by Binaural Fusion
Authors: Guttman N. , van Bergeijk W. A. , David E. E.
Published: September 2005

Some effects of monaural forward and “retroactive” masking were studied by means of binaural fusion. A pair of clicks was fed to one ear and a single click was delivered to the other at a low repetition rate. The experimenter controlled the amplitudes of all three clicks and the relative arrival times of two. The subject, who controlled the arrival time of the remaining click, was instructed to obtain centered fusions. The stimuli were 100 μsec rectangular impulses passed through PDR-8 earphones. The results indicate that “retroactive” masking follows the theoretical latency vs intensity curve derived previously from binaural fusion experiments with high-pass clicks. Forward masking appears to be relatively independent of intensity.
Intensitive Determinants of Remote Masking
Authors: Bilger Robert C. , Hirsh Ira J.
Published: September 2005

In preliminary experiments it was observed that the amount of remote masking that appears for low frequencies in the presence of high-frequency noise was dependent upon band width in the noise. To specify this relation two series of noise bands were used; one with a lower cutoff at 1000 cps and upper cutoff at from 1500 to 5000 cps, and the other with a lower cutoff at 2000 cps and the upper cutoff at from 2500 to 6000 cps. In both series the band width was increased in 3-db steps and the resulting bands were presented at various combinations of spectrum level and over-all level. The results indicate that: (1) with spectrum level held constant, remote masking increases directly with band width; (2) with over-all level held constant, remote masking varies inversely with band width; with band width held constant, remote masking increases with over-all level (or spectrum level). The slopes of relations (1) and (2) equal one, while the slope for relation (3) equals two.
Noise from Cavitation Generated by Vibrating a Mass of Water
Authors: Benjamin T. Brooke
Published: September 2005

A new method has been used for the study of noise arising from the collapse of cavitation bubbles. Isolated vapor bubbles were formed in de-aerated water undergoing vertical vibrations of about 1/30 sec period, whose amplitude was sufficiently large for the water to be in tension for part of the cycle. The bubbles were initiated from minute gas nuclei released by electrolysis at a certain instant each cycle; consequently, a long succession of identical bubbles was produced, each of which repeated the same sequence of growth, collapse, and several rebounds, and then disappeared before its successor became due. The noise pulse could conveniently be examined by displaying a hydrophone signal on an oscilloscope adjusted for fast single-sweep operation but triggered repetitively (by the signal from a second hydrophone placed nearer the noise source) at the frequency of bubble formation. The pulse was found typically to have a duration of about 10 μsec, and under certain conditions to undergo steepening such as to develop a shock front of duration considerably less than 1 μsec.
Vowel Amplitude and Phonemic Stress in American English
Authors: Lehiste Ilse , Peterson Gordon E.
Published: September 2005

Many different instrumental techniques for deriving an energy property of the speech wave have been employed in communications studies. There is as yet, however, no universal method of calculating the loudness of the various types of complex and quasi-random sounds that appear as time functions in speech. This paper does not present a method of making such loudness calculations but suggests that any such method would be inadequate for deriving physical correlates of accent or stress judgments about speech. The study reports volume indicator and instantaneous amplitude observations on sustained vowels produced under various conditions of speech effort, and on vowels produced in cvc syllables in a carrier phrase with stress held constant. The untested theory is proposed that the perception of linguistic stress is based upon judgments of the physiological effort involved in producing vowels. The relative amplitude and spectrum of the vowel provide the chief basis for judgment of the physiological effort.
Interaction of Sound Waves with Electrons in Metals
Authors: Morse R. W.
Published: September 2005

Since Debye's early work on the specific heat of solids (1912), it has been realized that the random thermal motions of a solid can be considered as a spectrum of sound waves. In a metal these sound waves scatter conduction electrons, and thus the interaction between sound waves and electrons is fundamental in determining the transport properties of the metal, e.g., the thermal and electrical conductivities. Recently, it has been found that sound wave attenuation by electrons can be measured experimentally using ultrasonic waves at liquid helium temperatures. This paper will review the basic theory of the scattering of electrons by sound waves. Some of the recent ultrasonic experiments will be discussed with particular emphasis being given to their potential in understanding some of the fundamental properties of metals.
Interaction of Ultrasound and Dislocations
Authors: Granato A. V.
Published: September 2005

The structure-sensitive component of ultrasonic attenuation in crystalline solids is usually caused primarily by dislocations which oscillate under the influence of an ultrasonic shear stress. The properties of the attenuation and the accompanying elastic constant reduction are determined by the obstacles which limit the motion of dislocations. Available data are discussed in terms of current theories which are based on detailed models for the obstacles. Examples of the utility of ultrasonic methods in the study of point defect-dislocation interactions and of the use of such interactions to eliminate the attenuation are given from radiation damage and plastic deformation studies.
Acoustical Factors in Jet Airport Design
Authors: Eldred Ken
Published: September 2005

With the advent of commercial jet airline operations, increased importance must be placed upon acoustical considerations in airport design. This paper discusses the relationships between the noise resulting from commercial jet and propeller airliner operation, including takeoff, taxi and idle for various projected traffic densities, and the various airport building functional design criteria. Emphasis is placed on the integration of acoustical design with airport functional layout to assist in maximizing architectural freedom in building design and minimizing building noise reduction requirements. Methods are presented to assist airport designers in achieving these architectural objectives in combination with other objectives affecting passenger comfort, employee effectiveness, and problems in bordering residential areas.
Extant Problems in Analysis-Synthesis Telephony
Authors: Flanagan James L.
Published: September 2005

Efficient voice communication implies transmission of the minimum information necessary to specify a speech event and to evoke an appropriate response. Human speakers generate information at rates which are much less than the capacity of conventional telephone channels. This disparity has motivated considerable research in analysis-synthesis techniques for speech transmission. One premise is common to most of the analysis-synthesis schemes; namely, the transmission system should be constrained so that the appropriate message ensemble contains only the sounds of human speech. One attempts, therefore, to build into the communication link as many as possible of the constraints characterizing the production and the perception of speech. Further, one hopes to manipulate the parameters of the constraints with as few independent, low information-rate signals as possible. This paper attempts to review briefly the progress which has been made with analysis-synthesis telephony, and endeavors to appraise the current status of the research. It undertakes to suggest how recent work in speech production may find application in transmission systems, and to point up some of the problems confronting further development. Finally, it considers briefly the potentialities of simulating speech systems with digital computers.
Equivalent Circuit Representation of a Flexible, Porous Medium
Authors: Lang William W.
Published: September 2005

As an extension to the general investigation of sound propagation in a flexible, porous medium reported at the Fifty-fifth meeting [.J. Acoust. Soc. Am. 30, 670 (1958)], an equivalent circuit representation of such a medium has been developed. At low frequencies a flexible, porous layer which is rigidly backed and locally reacting can be represented by lumped circuit elements. The circuit studied here consists of two parallel branches, one representing the air enclosed by the structure and the other representing the structure itself. From the specific acoustic impedance of this circuit, the percentage of incident sound energy absorbed at a flexible, porous surface is determined for a range of values of the significant physical constants which characterize the material. Coupling between the structural elements and the air enclosed by the structure is not described by such a simple circuit. The extent to which this simple representation describes the influence of nonrigidity on the sound energy absorbed by the porous surface is discussed. [This work was supported in part by the U. S. Army (Signal Corps), the U. S. Air Force (Air Research and Development Command), and the U. S. Navy (Office of Naval Research).]
Analysis of Flared Acoustic Matching Sections
Authors: Holte J. E. , Lambert R. F.
Published: September 2005

An analysis of flared acoustic matching sections is presented which considers the energy transfer problem from a reflection coefficient point of view. Relationships between the flare properties of the section and the frequency transmission characteristics will be discussed which permit optimum design of matching sections when the transmission band is prescribed and the impedance ratio at the ends of the section is not large. Effects of distributing the reflections along the sections in various ways will be considered. The inherent limitations set by the impedance mismatch upon the frequency transmission characteristics will be discussed. An analysis for large impedance mismatch obtained by the use of an analog computer will be presented and comparisons made between coupling sections having different transmission properties. Possible extensions of the theory to other applications will be mentioned.
A High Intensity Noise Facility
Authors: Tatge R. B. , Wells R. J. , Evans R. P.
Published: September 2005

A reverberant-type high intensity noise facility, using horn-type loudspeakers as sources, has been designed and built for environmental testing of missile components. A 120-cu-ft chamber is located inside a 3150-cu-ft room. Using bands of random noise as the input signal, a maximum sound level of 148 db has been produced in the small chamber; levels up to 140 db may be generated in the large room by opening the door of the small chamber. When driven by successive 13 octave bands of random noise with equal voltampere input to the loudspeakers in each band, the sound level is flat within ±5 db from 200 to 3150 cps. Under these conditions the standard deviation of sound levels in various positions in the small chamber relative to the mean sound level decreases from 4 db at 200 cps to less than 1 db at higher frequencies.
Riveting Noise Study
Authors: Kirchman E. J.
Published: September 2005

A study of riveting noise in the aircraft industry has been made. Octave band analysis led to a statistical survey, where variations in sheet, thickness, rivet diameter, and Bucking bar were tried. Although design consideration will prevent us from eliminating major noise sources, some limited data are available in controllable factors which have significant influence on riveting noise level.
Serendipitous Effects of Masking Noise upon Sensations Produced by the Dentist's Drill
Authors: Gardner Wallace J. , Licklider J. C. R.
Published: September 2005

The observations to be reported were made in a dentist's chair. Part of the sensory stimulation was generated by the dentist and his dental equipment, particulary his drill, during the course of routine dental operations. Part was generated by apparatus consisting of random noise generator, low-pass filter, stereophonic tape playback, patient-operated faders and attenuators, power amplifiers, and earphones. The initial observations concerned masking of the drilling noise. Low-pass random noise sufficiently intense to mask the drilling noise completely turned out not to be itself objectionable. Not only the sound of the drill, but also much of the massive complex of tension, anxiety, and pain was drowned in the masking noise. One patient {JCRL) made subjective observations, during a single drilling, alternately with and without the masking noise. During the masking noise, there was only a “small, thin sensation of pain.” When the masking noise was off, the noise and vibration of the drill accrued to the core pain and made it seem larger and more noxious. Further tests were made with music, and with music and noise in combination. Music is less effective than noise as a masker, but it is very effective in inducing relaxation. The combination of music and noise, alternating under the patient's control, appears to provide a practicable dental analgesia. Observations on more than 170 patients will be described, and applications outside the field of dentistry will be mentioned.
Reverberation Formula Which Seems to be More Accurate with Nonuniform Distribution of Absorption, with Field Examples of its Application
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. Through extensive tests made in a large number of rooms, where distribution of sound absorption varies widely in uniformity, an empirically derived formula is submitted. Photographs of graphic recorder decay curves, showing contrasts in predicted slopes, seem to confirm the validity of the formula. The recorder curves are records taken in the field. The data submitted are a small portion of an accumulation of measurements, covering a period of some five to six years, in rooms of widely varying volumes, widely varying boundary ratios, and marked dissimilarity in amounts of absorption and ratios of absorption distribution. This paper also includes a discussion of the new semicircular California Masonic Memorial Temple 3300-seat auditorium, recently completed in San Francisco, together with experiences with other rooms of difficult shapes. (This is an expansion of a paper, originally planned for the Washington meeting but not delivered.)
Transmission Loss of Single, Solid Walls
Authors: Watters B. G.
Published: September 2005

The transmission loss (TL) curve of a typical single, solid wall is characterized by (1) a 6-db per octave slope at low frequencies, (2) a “plateau” of nearly constant TL extending over two or more octaves of frequency, and (3) a 6-db or more per octave slope beginning above the plateau. The height in decibels of the plateau is determined by the modulus, density, and to a lesser extent, the loss tangent of the wall material. Thus, the plateau height, in decibels, may be thought of as a material constant and is independent of the wall thickness. In many practical instances (e.g., speech privacy between typical office spaces) the plateau TL is crucial. In such instances, small changes in the wall thickness (e.g., plus or minus a factor of two) may not have practical significance.
Ultrasonic Absorption Microscope
Authors: Dunn Floyd , Fry William J.
Published: September 2005

This paper constitutes a progress report on the development of an ultrasonic instrument for detecting microstructure. The principle of operation of the device, which is designated by the term “ultrasonic microscope” is as follows. The specimen is imbedded in a liquid, which closely matches it in acoustic impedance, and is irradiated with short pulses of high-frequency sound. Some of the ultrasonic energy is absorbed in the specimen and the reminder passes through it and excites a small probe placed immediately behind the region being investigated. As the specimen is moved relative to the sound source and the probe, in a direction normal to the direction of sound propagation, a varying acoustic signal will be detected by the probe since different amounts of acoustic energy will be absorbed by the specimen in different regions due to nonuniformities in its structure. A two-dimensional array of such probes produces a two-dimensional “picture” of the structure of the specimen. Preliminary experimental results obtained with such a “microscope” operating at a frequency of 12 Mc/sec will be presented. (Supported in part by a grant-in-aid from the American Cancer Society upon recommendation of the Committee on Growth of the National Research Council.)
Ultrasonic Welding
Authors: Welkowitz Walter
Published: September 2005

This paper will discuss the design of ultrasonic transducers necessary to produce efficient spot and seam welding. In addition, there will be a discussion of experience encountered with ultrasonic welding in the laboratory and in the field. Photographs and photomicrographs of metals welded ultrasonically will be presented. There will be a discussion of some of the physical mechanisms which must be involved in the bonding of metals by vibratory action.
Analysis of the Functions Served by a Loud Auditory Signal in Maintaining Alertness
Authors: Knaff P. Robert , Pollack Irwin
Published: September 2005

In a previous experiment, it was shown that detection performance during periods of sustained monitoring was significantly improved by sounding a loud auditory signal whenever an observer failed to detect a target. This experiment presents an analysis of the functions served by the signal. Each of five observers served for fourteen 90-min sessions in which the task was to detect a momentary change in brightness in a small light bulb. Targets were presented at an average rate of 48 per hour. Four experimental conditions were employed: (1) a loud (115 db) auditory signal contingent upon failure to detect a target, (2) a soft (75 db) adultery signal contingent upon failure to detect a target, (3) a loud auditory signal sounded at random times during the monitoring session, and (4) a “neutral” control condition. Analysis of the results indicates that conditions (1) and (2) above result in significantly improved performance over the control condition. Condition (3) above, however, is associated with significantly poorer performance.
Perception of Damped Sine Waves
Authors: Capraro Rene , Halle Morris
Published: September 2005

This paper discusses the perception of resonant frequency shifts in damped sine waves as a function of the time and magnitude of the shifts. The relation between the perception of the changes in frequency and damping of the wave form is also investigated. The interest in this study stems from the fact that changes in formant frequency (transitions) constitute an important class of cues in speech. The equipment producing the proper stimuli has been built and perceptual tests have been run testing a number of possible hypotheses.
Detection of Gated Sinusoids in White Noise as a Function of Frequency
Authors: Green David M. , McKey Mary J. , Licklider J. C. R.
Published: September 2005

Aural detection of 0.1-sec segments of pure tone in white noise was measured at sixteen frequencies, 250, 500, 750,⋯4000 cps, with a two-interval, forced-choice procedure. The measure of the listeners' performance in detecting the signals was the ratio (E/No) of the signal energy to the noise power density that was required for 75% correct response. The results of this experiment with fixed-duration segments of tone are compared with those of other studies which employed tones of indefinite or extended duration. The detection of a compound signal synthesized by adding together the sixteen harmonics of 250 cps was also measured. The individual harmonics were so adjusted in amplitude as to be equally detectable. The results are related to a model of summation over frequency. [This research was done in part under a National Science Foundation Fellowship and in part under Air Force Contract AF 18(600)-1219.]
Headset Microphone for Communication in Noise Fields of 135 db and Higher
Authors: Ware E. R. , Carrell R. M. , Touger M. L.
Published: September 2005

A headset microphone is described which will give a calculated 84% word articulation in a noise field of 140 db, such as may be found during trimming operations on jet engines and at missile test stands and launching sites. The M-87/AIC microphone and H-143/AIC earphone described at the May, 1958 meeting are employed with a noise shield and a specially designed ear cushion is a hard shell, circumaural type with a grease-filled sealing pad. The internal volume is divided by a flexible plastic sheath which lays loosely against the auricle and couples the earphone to the ear with a cavity of approximately 10 cc. The sheath is perforated with a few small holes which couple the larger volume of the shell to the ear in order to obtain increased attenuation below 500 cps. The acoustic isolation of the sheath above 500 cps also minimizes the effect of standing waves in the larger cavity upon the response and attenuation characteristic of the headset. The articulation performance cited above is estimated assuming 200-mw power available with 10-db peak clipping. This can be obtained from the AN/AIC-17 interphone system used by Air Force ground crews. Indicative articulation scores for jet noise fields up to 160 db, and tolerable exposure times based upon WADC damage risk criteria, are reported. [The work was supported by Contract AF 33(600)-33172 from WADC Communication and Navigation Laboratories under the direction of T. P. Mountz.]
Detectability of Small Irregularities in a Broad-Band Noise Spectrum
Authors: Malme Charles I. , Stevens Kenneth N.
Published: September 2005

The detectability of small changes in the energy content of a narrow frequency band in an otherwise white noise spectrum is measured using standard psychoacoustical testing techniques. The test stimuli are obtained by passing a white noise spectrum (100 cps-10 kc) through a filter having a simple resonance and antiresonance. The positions of the corresponding pole and zero in the transfer function are varied to produce either a peak or notch (alone or simultaneously) in the output spectrum. The band width and center frequency of the resulting irregularities are specified in terms of the positions of the poles and zeros in the s-plane plot. The stimuli are presented to the subjects by earphones having a relatively flat frequency response throughout the range of interest. The experimental results show the magnitude of a generally detectable spectrum irregularity as related to the pole and zero position in the transfer function of the filter. For example, a spectrum notch centered at 1000 cps requires a band width of about 130 cps to be detectable by an average listener when compared with the flat noise spectrum. This corresponds to a zero at s=−420±6280 sec−1 in the filter transfer function. The application of the experimental results to determine the amount of frequency response irregularity allowable in high-fidelity loudspeakers is discussed. Other possible applications in the field of speech research and audio engineering are enumerated. (This work was supported in part by the U. S. Navy, Office of Naval Research.)
How Much Ear Protection?
Authors: Weinreb L. , Touger M. L.
Published: September 2005

The proposed ASA Standard “Method for the Measurement of The Real-Ear Attenuation of Ear Protectors at Threshold”—Z24.22/406, which is currently being considered for adoption, specifies the use of threshold shift techniques. It has been observed in our laboratory during extensive evaluation of developmental ear protective devices over the past ten years that large differences in attenuation are obtained when using different attenuation measuring techniques. In addition, these differences vary for the different type of protector being studied. In this study four grossly different types of protectors are measured. These protectors differ in volume under the protector and in the principal sound transmission path at low frequencies. The protective devices included (1) HS-33 headset using the MX-41 muff, (2) H-70C/AIC headset using the MX-2088 muff, (3) RCA “Quiet-Ear” protector, and (4) RCA experimental ear protector. The attenuation methods employed are (1) threshold shift using a Békésy type audiometer, (2) loudness balance at approximately 60-phon level, and (3) objective method using a miniature microphone. The test subjects and room environment are the same for all types of measurements. A discussion of the differences in attenuation values obtained from the three methods will be given. [Supported in part by the U. S. Air Force under Contract AF 33 (600)-33172.]
Characteristics of Clarinet Tones
Authors: Kent Earle L. , Hall Jody C. , Lazure Richard P.
Published: September 2005

Extensive tests were made to determine the characteristic differences between clarinet tones judged by musicians to be acceptable or unacceptable. A research committee from the College Band Directors' National Association collaborated in the evaluations as well as other musicians in many sections of the United States. It is indicated that musicians are generally in close agreement and their subjective ratings are largely determined by the harmonic content of the tones. Tape recordings and a tone analyzer will be used in presenting the paper.
Studies of Cup-Mouthpiece Tone Quality
Authors: Kent Earle L. , Lazure Richard P.
Published: September 2005

Tests reported at the Fifty-First Meeting of the Acoustical Society of America on the characteristics of cornet tones have been extended to other instruments which use a cup mouthpiece. The trends indicated by the cornet tone quality studies are shown to be followed by the other instruments also. The instruments are found to have formant-like characteristics which exercise control over the harmonic content of the tones produced and help the listener in identifying the instrument producing the tones. Tape recordings and a tone analyzer will be used in presenting the paper.
Effect of Mutes on Cornet Tone Quality
Authors: Hall Jody C. , Lockwood Clyde E.
Published: September 2005

Tests reported at the Fifty-First Meeting of the Acoustical Society of America on the characteristics of cornet tones have been extended to include tones produced with various types of mutes. It is shown that the mutes modify or change the characteristics of the cornet sound. The muted sounds are found to have formant-like characteristics which are individual to the particular mute which is used. Tape recordings and a tone analyzer will be used in presenting the paper.
Formulas for the Computation of Sound Velocity in Sea Water
Authors: Mackenzie K. V.
Published: September 2005

Formulas are presented, which were derived from Kuwahara's tables. These formulas when programed on the Datatron have speeded up computations. The equations are in terms of temperature, depth, salinity, latitude, and the interaction of the temperature, salinity, and depth. Some recent long-path measurements were made with excellent supporting oceanography for the purpose of determining how well the long-path sound velocity can be computed with the equations. The long-path measurements have a precision of slightly better than one part in a thousand. This is roughly the uncertainty of the computed long-path sound velocity because the oceanographic parameters vary along the path and are never known in complete detail. There is fair agreement between the measured and the computed velocities.
Long-Range Sound Propagation in the Deep Ocean
Authors: Hale F. E.
Published: September 2005

The well-known SOFAR channel manifests itself in modified form for sound sources situated off axis. Sources are usually closer to the ocean surface than to the axis, and in such cases high-intensity “convergence zones” may appear at spacings of some 20 to 35 mi depending on latitude and on velocity conditions. Formed usually by deep “refracted-surface reflected” rays the caustic structure of a zone is known. These convergence zones are analogous to the zones of sound which alternate with zones of silence in abnormal sound propagation through the atmosphere. Recent publications giving the ray theory and specific details of the uw sound propagation have created a situation in which both much and little information is available. So that this situation may be relieved, a review of both experimental and theoretical efforts will be attempted. These efforts were carried out by both government and contracting laboratories. Accomplishments in recent years have shown that convergence zone propagation is common and predictable. Methods of fairly precise intensity computation exist but entail considerable effort. The existing computations, theory and experiments provide enough information so that convergence-zone propagation in the first several hundred mile range interval can be adequately described. Merging and confusion of zones is to be expected at greater ranges.
Shear Damping Treatment Involving Spacer-Foil Configuration
Authors: Ross Donald
Published: September 2005

The damping effectiveness of a treatment utilizing the shear motion of a viscoelastic layer depends upon the stiffness of a constraining layer and the separation of the center of the constraining layer from the center of the base plate. A treatment which increases the latter factor through use of a spacer has been described previously by Kerwin [J. Acoust. Soc. Am. 31, 846(A) (1959), and Paper IC3 presented at III International Congress on Acoustics, Stuttgart, Germany, September 1, 1959]. An alternative method of achieving large separation is to combine the function of the spacer with that of the constraining layer in a “spacer-foil.” The theory for such a treatment is given in the present paper, with relationships for the optimum thickness as a function of material properties.
Multidimensional Scaling Approach to the Determination of Basic Psychological Parameters for Pure Tones
Authors: Peters Robert W.
Published: September 2005

The multidimensional scaling model of successive intervals was applied to investigate the dimensionality of auditory perception of pure tones. The stimuli consisted of 16 pure tones. Thirty-nine observers made distance judgments of similarity between stimuli. These interstimuli distances were analyzed mathematically to reveal the minimum number of dimensions necessary to account for the distances between stimuli. The results of the analysis indicated that two factors, pitch and loudness, were fairly well defined. A third factor, not as well defined, appeared to relate to pitch. The purpose of the study was to evaluate the multidimensional scaling method for use in auditory areas where the dimensions are not well known, and, since the anticipated dimensions, pitch, and loudness, were revealed, proposed use of the model in other auditory areas is supported. [This research was supported in whole by the U. S. Air Force under Contract No. AF 33(616)-3644, monitored by the Aero Medical Laboratory, Wright Air Development Center.]
Localization of Low-Frequency Tones
Authors: Moushegian George , Jeffress Lloyd A.
Published: September 2005

At the May, 1957, meeting of the Acoustical Society of America, we presented results on the localization of a 500∼ tone, using various interaural intensity and phase differences. The subjects matched the laterality of the tone with that of a wide band noise which they adjusted in interaural time difference. Data were presented relating interaural time and intensity differences with laterality. The present study employs the same technique and extends the findings to other frequencies. The results indicate that time can be traded for intensity in the localization (or lateralization) of low-frequency tones, but that the trading factor is subject to large individual differences.
Cueing as a Determiner of Apparent Variability in Sensitivity
Authors: Shipley Elizabeth F.
Published: September 2005

The groupings of correct and of incorrect responses in psychophysical experiments have been attributed to changes in sensitivity. This paper suggests another way of accounting for such data. It is hypothesized that a given trial can offer cues to the nature of the stimulus. The adequacy of the cue is presumably determined by the effective stimulus intensity. Stronger stimuli should provide on the average better cues than weaker stimuli. Also trials on which correct responses are made should offer better cues than do incorrect trials. Thus correct responses should follow correct responses. Data were collected in a two-alternative forced-choice detection experiment in which a strong and a weak signal were presented at random. The proportion of correct responses was higher following correct responses to the strong signal than following correct responses to the weak signal. This is consistent with the notion that the adequancy of the cues on preceding trials influences the probability of a correct response. The opposite results would be expected if only fluctuations in sensitivity are involved since a correct response to a weak signal implies a greater average sensitivity than a correct response to a strong signal. [Supported by U. S. Air Force Contract No. AF19(604)-1728, monitored by Operational Applications Laboratory, Cambridge Research Center, and by U. S. Army, (SC) U. S. Air Force (OSR, ARDC), and U. S. Navy (Office of Naval Research)].
Excitation, Detection, and Applications of Hypersonic Waves
Authors: Bömmel H. E. , Dransfeld K.
Published: September 2005

A new method for the generation and detection of ultra high-frequency sound waves has been recently described [H. E. Bömmel and K. Dransfeld, Phys. Rev. Letters 1, 234 (1958)]. It is based on piezoelectric surface excitation at the ends of a quartz rod placed between two identical microwave cavities. Longitudinal as well as transverse waves have been generated this way and have been transmitted into other media by means of compressional bond techniques. This method together with the simultaneously discovered fact that the attenuation of hypersonic waves in quartz is very small at temperatures below 15°K should make it now possible to extend ultrasonic research up to frequencies of about 1011 cps. It should allow to investigate problems in solid state and liquid state physics involving phonon-phonon interactions, the interactions of phonons with spins, electrons, rotons, etc., at frequencies approaching those of the thermal phonons at low temperatures. Surface excitation should not be restricted to piezoelectric materials but should also be applicable to magnetostrictive substances as for example in ferromagnetic resonance. The results of hypersonic absorption measurements as a function of temperature in natural, synthetic, and neutron irradiated quartz crystals in the frequency range between 1000 and 4000 mc/sec will be presented.
Acoustic Measurements in Deep Water Using the Bathyscaphe
Authors: Lomask M. R.
Published: September 2005

In the summer of 1957, a series of dives for scientific purposes was made by the Bathyscaphe in the Tyrrhenian Sea off the west coast of Italy. Dives were made to 1000 meters and 3000 meters depth. This paper presents the results of the Hudson Laboratories part of the program, which consisted of low-frequency (10–400 cps) acoustic measurements of ambient noise and of propagation from a surface source. The noise spectra are observed as a function of depth and sea state and are found to be relatively independent of depth in zero sea state and to increase approximately linearly towards the surface in sea state 2, the rate of increase being greater for frequencies over 60 cps than below 60 cps. Vertical profiles of the sound field from a surface source were taken at ranges up to 7 miles from the source. The energy at 7 miles is found to be concentrated in the deep sound channel, while at 3 miles no such concentration is observed. Finally the use of the Bathyscaphe for acoustic work in general is evaluated. (This work was supported by the Office of Naval Research.)
Sound Propagation in Shallow Water
Authors: Ruff George A.
Published: September 2005

A knowledge of the sound field and of sound propagation in shallow water has great value in predicting long-range propagation and in calibrating sound receivers and generators. In this study intensity measurements were made at the Ordnance Research Laboratory's Calibration Station at Black Moshannon Lake which, though very shallow, has an extensive shoreline. These measurements were obtained for both fixed distances and variable depths and for fixed depths and variable distances. Special attention has been given to the study of the interference field caused by bottom and surface reflections over a wide range of frequencies. The measurements have also been used to estimate the sound adsorption caused by the proximity of the bottom, and results of this study are compared with the existing theory.