bluuebunny/crossref_metadata_2025 huggingface dataset:
Pulsation Oscillations of Cavities in Rubber
Authors: Meyer Erwin , Brendel Klaus , Tamm Konrad
Published: September 2005

The oscillation behavior of a spherical cavity in an infinite elastic medium is calculated for the case of an incident spherical dilatational wave entirely reflected at the cavity walls. It is shown that there exists for every Poisson's constant 0⩽σ⩽0.5 a frequency for which the amplitude of the oscillating cavity walls becomes a maximum. It is also shown that the amplitude resonance curves are symmetrical and that, assuming loss-free material, they have a finite half-width, which is caused by radiation losses and depends only on the ratio of shear wave and dilatational wave velocity.

Pulsation oscillations of spherical, rotational-elliptical, cylindrical, and cubic cavities in rubber blocks were examined experimentally. The pulsation oscillations were excited by means of a sound source coupled to the surface of the rubber block. The sound pressure inside the cavities was measured with a probe microphone. The experimental results for spherical cavities are compared with the theory. Good agreement is found with respect to the resonance frequencies.
Some Experiments concerning the Hole and Ring Tone
Authors: Chanaud R. C. , Powell Alan
Published: September 2005

Discrete-frequency tones can be generated when objects obstruct the path of an axially symmetric jet. An experimental study of this phenomenon was conducted when the objects were (1) a flat plate perpendicular to the jet axis, there being a hole in the plate of the same diameter as the jet orifice and concentric with the jet, and (2) a ring whose plane was perpendicular to the jet axis and whose diameter was equal to that of the jet orifice. The tone from the former geometry is the hole tone and that from the latter, not previously observed, is the ring tone. The mechanism of tone generation appears to be very similar to that of the edge tone, although presently only qualitative explanations can be offered for certain aspects of the phenomena. The axially symmetric jet systems are sensitive to very weak acoustic reflections.
Random Bearing Errors in Split-Beam Systems
Authors: Usher Theron
Published: September 2005

The performance of a linear array of 2M transducers in determining the bearing of a plane-wave random signal in a background of isotropic random noise is considered. The processing the array is arranged by means of wide-band phase-shifting filters and infinite clippers to produce a null response when the array is “on target.” Expressions for the angular uncertainty of the null response are derived, and the filter parameters that minimize this bearing uncertainty are determined. An expression for the minimum bearing uncertainty is also derived for arbitrary signal and noise spectra and also for a case employing well-known models for signal and noise spectra. The bearing uncertainty of a system with simple filter characteristics determined and compared with the minimum bearing uncertainty.
Minimizing Damage from Random Vibration
Authors: Mains R. M.
Published: September 2005

Damage is defined and examples are cited. Illustrative problems of relay contact arm chatter, gyro precession and noise generation, and stress fatigue in a structure are given. It is concluded that there are three means by which damage can be reduced: raising the damage threshold of the item, modifying the transmissibility of the intervening structure, or reducing the severity of the excitation. The examples are an attempt to show specifically how this can be done in practical cases.
Theory of Howlback in Reverberant Rooms
Authors: Waterhouse Richard V.
Published: September 2005

The theory of the howlback of a sound system in an enclosure is discussed. The influence of the Q of the enclosure modes on the howlback is considered, and various methods of controlling the howlback are reviewed.
Temporary Threshold Shift, Auditory Sensory Deprivation, and Conductive Hearing Loss
Authors: Katz Jack
Published: September 2005

A +15-dB per-stimulatory shift was noted at 6000 cps in 10 subjects with conductive hearing loss. In another pilot study, median shifts of +12 to +16 dB were noted at 6000 cps in 4 sophisticated listeners under conditions of auditory sensory deprivation.
Re: Audiometric Zero
Authors: Riley E. C. , Sterner J. H. , Fassett D. W. , Sutton W. L.
Published: September 2005

This Letter proposes calibrating audiometers in physical units (SPL) rather than in units referred to stone, more or less, arbitrary audiometric zero.
Vibrations of a System with a Finite or an Infinite Number of Resonances
Authors: Skudrzyk Eugen J.
Published: September 2005

The study is based on the general differential equation of a mechanical system. Driving force and solution are expressed as a series of natural functions of the dissipationless system. Dissipation is taken into account by introducing complex elastic constants. Each Fourier coefficient of the driving force is written as the product of an excitation constant and the total driving force. The excitation constants can then be included in the mode parameters of the system and the solution, written as the product of the total driving force and the “mechanical impedance” of the system. The solution is exact and useful at the lower frequencies. A simple solution for higher frequencies can be derived by replacing the series by an integral and evaluating this integral. Three important parameters can thus be obtained: the driving-point impedance that describes the velocity of the driving point and the reaction of the system to the driving force, the effective impedance that represents the average velocity amplitude over the system, and the effective dissipation resistance with respect to this average-velocity amplitude.

The expression derived for the high-frequency driving-point impedance then turns out to represent, also, the general background level at lower frequencies. The solution for the driving-point impedance in the intermediate frequency range is obtained by adding to this background the contribution of the natural mode that has its resonant frequency closest to the frequency of the force; the effective impedance, on the other hand, is given with good approximation as the impedance of the mode whose resonance frequency is closest to the frequency of the force; and the effective dissipation resistance is given by the resistive component of this mode impedance.

The mode parameters are computed for rods, membranes, plates, and shells for three situations—a point force, a linear force distribution, and a force distribution given by a Fourier integral. The results make it possible to handle complicated mechanical systems with almost the same ease as simple mass points, and to compute their sound radiation.
Measurement of Speech Spectra Recorded with a Close-Talking Microphone
Authors: Harris Cyril M. , Waite William M.
Published: September 2005

The Long-time average (100 sec) power spectral densities of speech recorded with a close-talking microphone are presented for 7 male talkers and 5 female talkers. The average lip to-microphone distance was approximately 58 in. and a breath shield was used. These data were obtained with an analyzer counting of a bank of 54 contiguous Gaussian filters whose scanned output was written on magnetic tape for subsequent computer processing. The processing program obtained the mean-square amplitude in each filter band and converted it to decibels, with appropriate corrections for filter bandwidth.
Method for Evaluating Transducer-Loading Effects on Ultrasonic Transit-Time Measurements
Authors: Kammer E. W.
Published: September 2005

An ultrasonic-measurement technique and data-processing scheme are described in which time intervals are measured between transducer resonance oscillations within the structure of successive unrectified echos rather than between echo leading edges. When plotted against the transducer resonance period, these time intervals determine a family of straight lines that have a single point in common at zero transducer resonance period. It is propo-ed that the transit time associated with this common point is the true travel time for sound in the medium unperturbed by transducer effects.
Discussion of: “Effect of Bending on Vibrations of Spherical Shells”
Authors: McIvor Ivor K. , Sonstegard David A.
Published: September 2005

Association of Kalnins' bending modes with a large percentage of bending-strain energy is dependent on the thickness-to-radius ratio and the mode number.
Reverberation Chamber Study of the Sound Power Output of Subsonic Air Jets
Authors: Waterhouse Richard V. , Berendt Raymond D.
Published: September 2005

The reverberation chamber technique was used to determine the sound spectra and acoustic power radiated by air jets over a range of subsonic velocities. Different air jets were used with round and square velocity profiles; nozzles of circular cross section, and nozzles with saw-tooth and corrugated ends were also used. Of these nozzles only the latter type gave a significant (9 db) reduction in sound power output for a given exit-pressure ratio. A study was made of the limitations of the reverberation chamber technique caused by the absorption in the chamber. When this absorption became considerable, the measurement of sound pressure level in a circle around the sound source revealed a directional pattern, and the assumption of uniform energy distribution in the chamber became invalid. This situation was noticeable at frequencies above 5 kc in the National Bureau of Standards chamber, owing to air absorption.
Forced Motion of a Thin Bonded Plate
Authors: Jones John P.
Published: September 2005

In many cases of interest to experimentalists and geophysicists, the situation exists where a light, thin layer of material, such as glue or adhesive, is bonded to a heavier structure. If the layer is thin enough and if its acoustic impedance is small as compared to the underlying structure, then the layer can be thought of as having little effect upon the motion of the substructure. Thus, the effect of the substructure is to force motion of the thin layer. This paper considers the dynamic problem of a thin layer forced by displacements on the lower face and tractions upon the upper face. The exact solution is derived for the two-dimensional case, while the three-dimensional case is first considered using Bernoulli-Euler-Kirchhoff plate theory and, after this, including the effects of shear deformation and rotatory inertia. It is found that, if shear deformation and rotatory inertia are included, the theory is fairly accurate for problems in which the quarter-wavelength of the disturbance is greater than or equal to the plate thickness.
Occurrence of Wave Effects in Rubber Antivibration Mountings
Authors: Snowdon J. C.
Published: September 2005

An approximate theory of rod vibration given Love has been extended to describe the occurrence of wave effects, or wave resonances, in rubber antivibration mountings. Thus, the longitudinal vibration of a mass-loaded rubber mount of significant lateral dimensions and uniform cross section has been determined with the assumption that the elastic modulus and damping factor of the rubber are frequency- dependent quantities. Knowledge of the manner in which the elastic modulus and damping factor of natural rubber, natural rubber filled with carbon black, and a high-damping synthetic rubber depend upon frequency has enabled realistic computations of transmissibility to be made. These computations have been contrasted with results obtained, for the same rubbers, from the simple one-degree-of-freedom theory in which the occurrence of wave effects is disregarded. The effectiveness of the natural-rubber mountings, which have relatively small clamping, is overestimated by the simple theory at high frequencies, although transmissibility will normally remain a small quantity. In the case of the high-damping rubber considered, the results of the simple and Love theories are in relatively close agreement.
Note on Vowel Duration Seen Cross-Linguistically
Authors: Zimmerman Samuel A. , Sapon Stanley M.
Published: September 2005

The influence of a following consonant on the duration of a tonic vowel in English raises serious linguistic implications. The present paper attempted to study the problem cross-linguistically using English and Spanish. Readings of word lists in the two languages based on pairs contrasting in terms of voicing revealed that the two languages are qualitatively similar but quantitatively different from the point of view of the duration of a vowel preceding a sonant. The over-all vowel range of Spanish is considerably less than that of English, and difference in duration related to sonants is also much smaller.
Approximation to the Array Signal-Gain Fluctuation Spectrum
Authors: Shapiro Arthur
Published: September 2005

It is known that the signal gain of an array of hydrophones fluctuates randomly in time. Several authors have investigated these fluctuations from different viewpoints; most of them determine mean-square array responses assuming correlated phase fluctuations. Since the signal gain varies with time, it should be regarded as a stochastic process. All attempts to find the multidimensional distribution functions of this process assuming Gaussian inputs have failed. It is not difficult, however, to develop an approximation for the power spectrum of the gain fluctuations of the array output in terms of the spectra at the individual hydrophones and the cross spectra between the array elements. Data were taken on the individual elements of an array of five hydrophones and the spectrum of the array gain variations was computed in accordance with the procedure given. This spectrum is compared with the spectrum obtained directly from the fluctuations of the array output. It is hoped that measuring array fluctuations in terms of spectra at individual hydrophones and cross spectra between hydrophones will give some insight into the mechanism causing the fluctuations.
Change in Acoustic Impedance Detected by Nuclear Induction
Authors: Jennings D. A. , Tanttila W. H.
Published: September 2005

The change in impedance of a sodium chloride rod due to change in frequency of the driving quartz crystal is detected by nuclear induction.
Studio For Listening Tests
Authors: Dolanský Ladislav O.
Published: September 2005

In this paper the design, construction, acoustical testing, and articulation testing of a listening studio, giving reasonably constant listening conditions, is described. The reverberation time has been measured by several methods, and was found to be equal to about 0.5 sec. A comparison of the individual results is presented.
Can a Sensory System be Specified by Its Internal Noise?
Authors: Eijkman E. , Vendrik A. J. H.
Published: September 2005

The detection model is used to describe the detection of scarcely discernible noiseless signals by human observers. Detection is hampered by an internal noise generated by the sensory system itself. In the present study, it appears that increments of loudness of a tone and increments of intensity of a light can be detected independently and simultaneously. Here, the internal noise is specific for the system responsible for this detection. On the other hand, detection of an increment in duration of visual and auditory signals is completely correlated. This correlation and the similarity of the detectability of the two kinds of signals indicate that a “duration center” exists, serving to estimate the duration of both visual and auditory signals. The methods developed are useful for identification of separate or common parts of sensory systems.
Loudness of Periodically Interrupted White Noise
Authors: Pollack Irwin
Published: September 2005

The burst level of a periodically, abruptly interrupted, white noise, necessary to match a continuous noninterrupted white noise in loudness, was examined over a wide range of interruption conditions. A procedure for calculating the required burst level, with knowledge only of the time-intensity characteristics of the interrupted noise, is outlined.
Detectability Threshold for Combination Tones
Authors: Plomp R.
Published: September 2005

Experiments were performed on the detectability threshold for combination tones, defined as the sensation level of primary tones for which combination tones become audible. Investigated were (1) detectability threshold for h−l with (h−l)<<(h+l), where h and l are the frequencies of the higher and lower primary tone, respectively; (2) detectability threshold for 200, 400, and 600 cps with 800+1000 and 800+1400 cps as primary tones; (3) audibility of combination tones for l = 1000 cps and h variable between 1000 and 3000 cps; (4) detectability threshold for the “missing fundamental” of ∑ n−210 cos 2 πnft, with f varying from 125 to 1000 cps. From the experimental data, we may conclude that (1) there are large individual differences in the minimum sensation level of primary tones for which combination tones appear; (2) for usual listening levels of speech and music, the ear's distortion is sufficiently low to avoid audible combination tones; (3) the same holds for the “missing fundamental,” so the fact that the pitch of a complex tone without fundamental is equal to the pitch of this tone cannot be explained by the assumption that the fundamental tone is reintroduced in the listener's ear; (4) the fact that the detectability thresholds for combination tones are significantly lower for small than for large tone intervals indicates that, for both cases, the ear's distortion cannot be represented by the same nonlinear characteristic and supports the evidence that the tones are produced in the inner ear.
On the Propagation Velocity of Sound in the Human Skull
Authors: Zwislocki J.
Published: September 2005

Measurements of the propagation velocity of flexural waves in the human skull performed in three different studies are discussed and compared with each other. The analysis leads to the conclusion that the existing discrepancies may be due to individual differences in skull thickness. For frequencies around and above 1000 cps the highest measured velocity amounts to 570 m/sec and the lowest to 260 m/sec.
Theory for Psychophysical Learning
Authors: Schoeffler M. S.
Published: September 2005

A model for psychophysical learning is constructed by imposing some conditioning principles on concepts derived from the theory of signal detectability. The effects of a priori probability, feedback, and practice are derived in part by Monte Carlo simulation and in part by analysis. The theory makes some novel predictions for the effects of these variables, all of which find support in the literature. Some theoretical results are: (a) performance improves with practice; (b) feedback can be detrimental to performance in a psycho-physical task; (c) when the a priori probabilities of the stimuli are unequal and feedback is provided, the response criterion moves in the direction of optimality, but does not move far enough to reach optimality; however, when no feedback is provided, the criterion moves in the opposite direction.
Loudness Change of Pure Tones with Contralateral Noise Stimulation
Authors: Vigran Erik
Published: September 2005

Loudness change of pure tones is measured with contralateral stimulation of narrow-band noise. A “paired comparison” method was used, and an increase in loudness was found at tone SPL 80 dB in the applied frequency interval 300–1500 cps. The contralateral stimulus was 13-oct white noise with center frequency 2500 cps. A maximum loudness increase corresponding to 7–8 dB in SPL was found with noise SPL 100 dB. It is assumed that the measured effect can not be due to the middle-ear muscle reflex, but must be explained in terms of central interaction.
Dynamic Analog Speech Synthesizer
Authors: Rosen George
Published: September 2005

A dynamically controllable electrical analog of the vocal tract capable of synthesizing sequences of speech sounds is described. The acoustic transmission line between the glottis and lips in the human vocal tract is realized electrically by eleven electronically controlled variable LC sections plus three fixed sections. Each variable capacitor is realized by means of the Miller effect, and the inductors are saturable reactors. Both elements of each section are controlled by a single voltage in a manner that constrains the LC product to remain constant, and varies the ratio L/C to simulate changes in effective cross-sectional area. The analog can be excited by a buzz source to simulate the glottal tone, by a noise source inserted at various distances from the glottis to simulate the noise of turbulence, or by both together. Thus, vowels and most consonants can be produced with equal facility by the dynamic analog. Control voltages are derived from a resistance network in which a series of desired articulatory configurations is stored. A timing arrangement chooses the excitation and articulatory configurations in the proper sequence, and smoothing circuits are used to assure natural transitions from one configuration to the next.
Origin of Ultrasonic Volume Viscosity in Associated Liquids
Authors: Litovitz T. A.
Published: September 2005

Thermodynamic data on specific heat, and thermal expansion coefficient of glycerol in the liquid and glass state are used to investigate the origin of the ultrasonic volume viscosity losses and associated dispersion in liquid glycerol. It is shown that the volume relaxation effects cannot be accounted for on the basis of a thermal relaxation involving either the vibrational specific heat or the structural specific heat. It is concluded that the volume viscosity in glycerol (and most probably in all the associated liquids) has an origin similar to that found for water, namely, a relaxing isothermal compressibility.
On the Minimum Audible Angle
Authors: Mills A. W.
Published: September 2005

The difference limen for the azimuth of a source of pure tones was measured as a function of the frequency of the tone and the direction of the source. Tone pulses between 250 and 10 000 cps were sounded in the horizontal plane around the head of a subject seated in an anechoic chamber. The smallest angular separation that can be detected between the sources of two successive tone pulses (the minimum audible angle) was determined for each of three subjects. These threshold angles are analyzed in terms of the corresponding threshold changes in the phase, time, and intensity of the tone at the ears of the subject. A comparison of these thresholds with those reported for dichotic stimulation indicates that the resolution of the direction of a source is determined, at frequencies below about 1400 cps, by interaural differences in phase or time, and at higher frequencies by differences in intensity. When the conditions are optimal for temporal discrimination, the threshold for an interaural difference in time is about 10μsec, and when the conditions are optimal for intensity discrimination, the threshold for an interaural difference in intensity is about 0.5 db.
Device for Generating Surface Waves with Adjustable Speed
Authors: Wehrmann O. H. , Lundberg J. L.
Published: September 2005

A device for generating surface waves with a low propagation velocity in the frequency range between 5 and 100 cps is described. The waves are simulated by a number of small elements vibrating with a stepwise increasing phase relationship along the direction of propagation.
Use of Directional Probes for Nearfield Measurements
Authors: Lubfll Alan H.
Published: September 2005

The notion of using directional probes for facilitating nearfield measurements of underwater acoustic transducers is examined with the aid of the von Helmholtz form of the Huygens-Green equation. The use of directional probes to create a uniform plane-wave field within an enclosed volume, and, hence, replace a distant transducer for either generating a plane wave or monitoring the farfield behavior of a test transducer, seems very promising.
Temporary Threshold Shift as a Function of Noise Exposure Level
Authors: Trittipoe W. J.
Published: September 2005

Under special conditions, numerous investigators have observed that, when duration of exposure is held constant, a greater temporary threshold shift (TTS) may occur after exposure to a lower sound level than after exposure to a higher sound level. However, at least after a short recovery interval, it would be reasonable to expect that TTS following exposure to higher sound levels would be an increasing function of the exposure level. In the present study TTS was measured continuously with a Békésy-type audiometer at 4000 and 6000 cps for 10 min following a 3-min exposure to a thermal noise. Five different noise levels, ranging in 5-db steps from 108 to 128 db in SPL, were used. Among nine ears tested, twice on each condition, only one ear showed a pattern of decreasing TTS with an increased noise exposure level at both measuring frequencies.
Comments on Normal-Mode Theory
Authors: Marsh H. W.
Published: September 2005

Errors in a report of the author were mentioned by Pedersen and Gorden [J. Acoust. Soc. Am. 37, 105–118 (1965)] and are commented upon. Additional comments are given on the utility of normal-mode theory applied to surface-bounded layers.
On the Effect of Practice and Motivation on the Threshold of Audibility
Authors: Zwislocki J. , Maire F. , Feldman A. S. , Rubin H.
Published: September 2005

The thresholds of audibility for 100 and for 1000 cps have been measured on five groups of originally naive listeners by various experimental techniques. All the experiments showed improvement of the threshold with practice. The improvement was greater at 100 cps than at 1000 cps. Pretraining at 1000 cps did not affect the threshold change at 100 cps. The improvement of the threshold with practice was enhanced considerably by reward and feedback.
Pistonphone with Differential Piston
Authors: Merhaut Josef , Vlček Miroslav
Published: September 2005

The article first examines the various sources of error in absolute calibration of standard microphones in a pistonphone. A new differential pistonphone has been developed in the Czechoslovak Research Institute for Telecommunications which enables absolute calibration of microphones with the accuracy 0.1 db. The design and properties of the instrument are described.
Relative Intensities of Sounds at Various Anatomical Locations of the Head and Neck during Phonation of the Vowels
Authors: Moser Henry M. , Oyer Herbert J.
Published: September 2005

Speech signals from 16 different anatomical locations were recorded as subjects intoned different vowels at a constant level. Power level analysis was made to determine relative intensity of the signals. It was found that significant difference in intensity exists among the anatomical locations. Some locations of lesser intensity were subjectively evaluated as providing more faithful signals.
Aerodynamic Sound from Centrifugal-Fan Rotors
Authors: Chanaud R. C.
Published: September 2005

The sound powers of small uncased centrifugal-fan rotors were measured at low-tip Mach numbers. Correlation of the data by use of a similarity relationship derived from theory has shown that the broad-band rotor sound is a result of randomly oriented dipole sources caused by fluctuations in fluid momentum. Deviations of the dependence of sound power on speed from that theoretically predicted were found. Speed dependences less than that predicted can be explained as a nearfield effect; the lack of agreement between theory and the fan law for sound can be explained on the same basis. Observed speed dependences greater than that predicted appear to result from having fixed frequency limits on the measurement system. A sharp wedge placed near the rotor periphery was found to generate discrete-frequency dipole sound. Quadrupole sound appeared to be negligible.
Limits of Direct Speech Communication in Noise
Authors: Pickett J. M.
Published: September 2005

Person-to-person tests of sentence intelligibility were carried out in low frequency and white noise at noise levels ranging from 85 to 118 db. Talkers attained shouting levels of vocal effort but the maximum tolerable noise levels for 90% sentence intelligibility and 1 m between talker and listener were estimated to be 95 db for white noise and 105 db for low-frequency noise.
Speech Intelligibility at High Noise Levels: Effect of Short-Term Exposure
Authors: Pollack Irwin
Published: September 2005

Successive word intelligibility tests were executed at a constant S/N ratio over a 13-min period for a range of white noise levels between 45 and 130 db. Speech intelligibility declined over the test period as a result of continued exposure to noise levels of 115 db and higher. Interactions among different noise levels on successive tests, as evidenced by speech intelligibility scores in noise, was minimal when the noise levels were separated by less than 80 db.
Effect of Water Vapor on the Napier Frequency of Oxygen and Air
Authors: Henderson Malcolm C. , Herzfeld Karl F.
Published: September 2005

The Napier frequency (frequency of maximum absorption per wavelength) in oxygen and in air is shifted to higher values by water vapor according to a quadratic law that has different coefficients in the two cases. It is shown that proper treatment of the relevant equations leads to the correct experimental relationship between them. From this relationship, all the various velocity constants in the equilibrium equations may be determined numerically. It turns out that nitrogen has a somewhat stronger effect than oxygen on the relaxation of water vapor, and that the rate of resonant interchange of energy between oxygen and water vapor is, in fact, smaller than the rate of relaxation of water vapor by itself. It is also shown that the postulate of dimer formation in water vapor as an explanation of the quadratic relationship leads to a contradiction with experiment.
Interaural Effects upon Speech Intelligibility at High Noise Levels
Authors: Pollack Irwin , Pickett J. M.
Published: September 2005

The role of interaural effects upon speech intelligibility was examined at high noise levels. Over a wide range of conditions, a “mixed” listening condition (speech and noise to one ear and noise alone to the other ear) produced substantially lower intelligibility scores than monaural or binaural presentation of both speech and noise. The results are interpreted in terms of the interaction between the intelligibility of speech cross-conducted to the other ear and the apparent localization in space of the speech and noise.
Ultrasonic Dispersion in Oxygen
Authors: Connor James V.
Published: September 2005

The velocity of ultrasonic waves in oxygen was measured at 40.6°C and 2 Mc/sec, with pressures ranging from one atmos to 0.35 cm Hg. Velocity dispersion was found at the lower pressures and is accounted for in part by rotational relaxation and at the lower pressures by the onset of the Stokes type of dispersion. The midpoint of the dispersion curve lies at 122 Mc/atmos, which corresponds to a relaxation time of 21.76×10−10 sec and to 13 as the average number of collisions necessary for the energy exchange. Consideration of the added translational dispersion effect establishes 12 as the average rotational collision number. A Hubbard-type sonic interferometer was used together with a strip recorder, several different tuning techniques being employed at the lowest pressures.
Rôle of the Pinna in Hearing
Authors: Flynn William E. , Elliott D. N.
Published: September 2005

Behaviorally determined auditory thresholds of normal monaural cats were compared to those of pinnaless cats. The removal of the pinna resulted in a significant loss of hearing, particularly at the high frequencies. This loss is considered in terms of the pinna's function as a funneling device and of possible changes in the resonance characteristics of the auditory canal.
Cochlear-Microphonic and Summating Potentials and the Outputs of Individual Hair-Cell Generators
Authors: Whitfield I. C. , Ross H. F.
Published: September 2005

This paper examines the effects of abandoning the assumption that the summating potential (SP) and cochlear microphonic (CM) commonly recorded from the cochlea are produced by single groups of in-phase generators. It shows that, by postulating that the recording electrode averages the output of many out-of-phase generators, several of the apparently rather anomalous behaviors of the SP and CM may be explained. Included in this category is the behavior of the CM at very high intensities. A new mode of generation of the SP is suggested and some of its implications discussed. A semiquantitative argument is used to substantiate the claim that the mechanism of cancellation of out-of-phase components is adequate to account for those effects which have been attributed to it, and a concluding section deals briefly with some of the further implications of the model relating to other observed behaviors.
Surface Reflection of Sound at 100 kc
Authors: Pollak M. J.
Published: September 2005

Short sound pulses at 100 kc were transmitted over a 100-ft range in a shallow estuary. Surface-reflected signals were recorded separately from direct signals. Surface reflection was most pronounced in fall and winter when vertical sound-speed distribution produces upward refraction in the upper ten feet of water. In spring and summer the opposite conditions prevail. Eight one-minute records, consisting of about 1200 pulses each, were analyzed. When pulse amplitudes and their frequencies of occurrence were transformed into dimensionless units, it became feasible to combine all records into one frequency distribution diagram. Despite considerable scatter in the data, there is a marked resemblance to a Rayleigh distribution. This is to be expected on theoretical grounds.
Nearfield Pressure for a Steered Array of Strips
Authors: Mangulis Visvaldis
Published: September 2005

The nearfield pressure and the cavitation-limited power output of a steered array of infinite strips in an infinite rigid-plane baffle is calculated. The strips have the same velocity magnitude. The pressure distribution on the surface of the array is almost constant for an array steered to broadside, and it becomes undulatory as the array is steered away from broadside. When the strips occupy a large fraction of the total array area, the peak pressure occurs off the surface of the array for an array steered to broadside. Near endfire, for the same ratio of the strip areas to the total array area, small strips closer together have a lower peak pressure than large strips farther apart. The mutual-coupling coefficients and the radiation impedances of strips are also calculated. For an array steered to broadside or for an array with strip widths much less than a wavelength, one can find approximately the peak pressure magnitude from the magnitude of the maximum impedance.
Measurement of Auditory Thresholds
Authors: Brown A. E.
Published: September 2005

Two systems of measuring auditory masking thresholds by statistical psychophysical techniques are developed. The first is a succession of free-choice tests with a different level of presentation fixed for each test. In the second, the presentation level is automatically adjusted and maintained at a level close to threshold. Scoring of the two tests is developed and their interrelation is discussed. The customary use of ROC (receiver operating characteristics) notations in this type of psychophysical testing can be augmented to provide a more comprehensive measure of the over-all performance of a test subject. The term d′, developed by Tanner, Swets, and Green, provides a measure of the system under test to perform as an ideal receiver. This notation is augmented by a decision term D, which relates to the placement of the subjects' decision criterion and is independent of d′. When taken together, d′ and D define the response of the subject and show the effect of environmental changes. Alterations in environment produce changes in test results. These changes are assessed in terms of d′ and D, showing how it is possible to provide a sensitive psychophysical measure of environmental effects.
Neurophysiological Evidence for the Stevens Power Function in Man
Authors: Keidel W. D. , Spreng M.
Published: September 2005

Human evoked cortical responses to acoustic stimuli occurring within 150–170 msec after stimulus onset yielded input-output functions fairly comparable with Stevens' power functions from psychophysical experiments. The objective threshold and equal-loudness contours thus obtained were both in fair agreement with the well-known subjective measurements.
Proposal for an Explanation of Limens of Loudness
Authors: Pierce J. R.
Published: September 2005

It is proposed that the limen of loudness ΔS for pure tones is equal or proportional to the root-mean-square deviation in the number of pulses produced by the sound in the time T of observation. By making a plausible assumption concerning the deviation and by assuming that loudness S is proportional to the pulse rate one obtains ΔS = A−12T−12S12. Here A is a constant which must be a function of frequency if the equation is to fit experimental data. The fit is encouraging but not completely convincing. If valid, the hypothesis might be used to explain other acoustic phenomena.
Pitch Discrimination for Synthetic Vowels
Authors: Flanagan James L. , Saslow Michael G.
Published: September 2005

A psychoacoustic experiment to determine the just-discriminable changes in the fundamental frequency of synthetic vowels is described. The experimental parameters investigated are several combinations of four vowels (|i, æ, ɑ, u|), three sound pressure levels (60, 70, and 80 db re 0.0002 dyne/cm2) and two fundamental frequencies (80 and 120 cps). The results indicate that the just-discriminable changes in fundamental frequency are of the order of 0.3 to 0.5 cps, and are, in general, slightly less than the frequency changes discriminable a pure tone of the same frequency and sound pressure level. Application of the the results to speech compression is suggested.
Inverse Magnetostrictive Effect of Ultrasonic Stress Waves in Steel
Authors: Langenecker B.
Published: September 2005

The pronounced changes in the state of magnetization of ultrasonically, irradiated SAE 1019 steel are utilized to determine acoustic stresses, modes of propagation of 20-kc/sec ultrasonic-stress waves, and variations in these parameters as functions of acoustic energy density (⩽109 erg/cm3) superimposed static tensile stress (⩽1010 dyn/cm2), and temperature (⩽Curie point). The quantitative results from these studies are fundamental for research on the mechanisms of plastic deformation, zone melting, and fracturing of metal crystals by high-amplitude ultrasonic stress waves. The results also reveal potentials of inverse magnetostriction in investigations on magnetization, and relations between magnetostriction and Young's modulus, phase transition, and phenomena associated with the internal structure of the materials.
Nonlinear Acoustic Properties of Orifices of Varied Shapes and Edge Conditions
Authors: Thurston George B.
Published: September 2005

The results of a study of the effect of shape and orifice edge conditions the nonlinear acoustic properties of orifices are presented. The samples studied consisted of orifices of circular, rectangular, and square shape in thin orifice plates. Varied edge conditions considered are square, round, and symmetric and nonsymmetric beveled edges for circular orifices in thick plates. These samples were studied for sinusoidal volume velocity in the orifice. It is found that for all the symmetric samples the pressure contains odd harmonics while for the nonsymmetric sample a steady component and second harmonic component are superimposed on the odd harmonies. An equation for the pressure-flow relation is given which is applicable to both symmetric and nonsymmetric orifices.
Vibrational-Energy Transmission in a Three-Element Structure
Authors: Lyon Richard H. , Scharton Terry D.
Published: September 2005

The transmission of vibrational energy in a planar, three-element plate/beam/plate structure is analyzed. Theoretical predictions of average energy (or acceleration) ratios in frequency bands are developed, using concepts of energy flow in multimodal systems that have been described previously. Interstructure coupling parameters are calculated for torsional and flexural motions of the central connecting member (beam), and the energy transfer contributed by each type of motion is also calculated. It is found that the energy transfer is dominated by beam flexure in the lower-frequency bands, but torsional motion contributes significantly at the higher frequencies. Experimental analysis of a model of the structure is consistent with the theoretical predictions.
Response of Internally Damped Cantilever Beams to Sinusoidal Vibration
Authors: Snowdon J. C.
Published: September 2005

The response of internally damped cantilever beams to sinusoidal vibration is described theoretically. An expression for the magnitude of the force transmitted to the terminations of the beams is derived when both a primary and a secondary force are employed to excite the beams at arbitrary positions along their length. It is demonstrated that the transmitted force can be attenuated significantly through broad ranges of frequency when the primary and secondary forces are of equal magnitude and their location is chosen suitably. The effect of varying the relatively-phase angle between the driving forces is considered. The influence of the secondary force upon the driving-point impedance that is presented to the primary force at a separate location is also discussed. Consideration is given to the magnitude of the force transmitted across a beam when a single driving force excites the beam at its free end and the beam is mass-loaded, in turn, at its free end, at its midpoint, and simultaneously at its free end and at its midpoint.
Acoustical Design of the Alberta Jubilee Auditoria
Authors: Northwood T. D. , Stevens E. J.
Published: September 2005

Two large auditoria have recently been built by the province of Alberta, Canada, in the cities of Edmonton and Calgary. The main auditoria, which seat 2700 persons, are designed for both concert and large-scale stage presentations. This paper reports on the design and on the extensive acoustical testing in the laboratory and in the halls themselves. Impedance tube and reverberation chamber data were obtained for materials and components of the auditoria. Reverberation time, pulse tests, and other objective measurements were made in the halls as they approached completion. The project culminated a test concert attended by about 1800 people, including 11 expert observers who afterward participated in a discussion of the acoustical properties of the hall.
Influence of Relative Changes in Magnesium and Sulfate Content upon the Sound Velocity of Sea Water
Authors: Lord Norman W. , Ransone Morris A. , Brey Mary E.
Published: September 2005

A set of nine solutions whose chemical composition is approximately that of sea water has been studied for its sound-velocity temperature dependence at atmospheric pressure. The compositions differ drastically from one another in their proportions of magnesium and sulfate ions, but all have the same total weight of dissolved solids. Final results enable one to estimate the effect upon sound velocity of the small differences in chemical composition that have been shown by the recent work of Cox to exist in typical sea water. The effect is quite small and is minimized best by using a measure for salinity that reflects the total weight of dissolved solids. It is shown that, among the compounds making up sea water, their contributions to its sound velocity bear roughly similar proportions to their contribution to its salinity.
Temporary Threshold Elevation Produced by Continuous and “Impulsive” Noises
Authors: Spieth Walter , Trittipoe William J.
Published: September 2005

Three experiments compared the amounts of temporary threshold elevation resulting when a given total amount of noise energy was presented to the ear in the form of repeated, short, intense bursts, and in the form of continuous noise (of much lower maximum intensity). Several patterns of noise bursts were tested, as well as continuous noise. One-millisecond noise bursts and continuous noise, of 20 min duration, were tested most extensively. The most severe impulsive noise tested consisted of 1-msec bursts every 10 msec for 20 min, with a burst SPL of 127 db or long-time-average level of 117 db.

It appeared quite conclusively that 1-msec bursts of noise have considerably less effect than the equivalent amount of continuous energy on thresholds at 3000, 4000, 6000, and 8000 cps. Noise bursts of 10 msec, 100 msec, and 1 sec length were tested less extensively; it appears that they would cause no more threshold elevation than would the equivalent amount of continuous noise.
Caustics and Convergence Zones in Deep-Water Sound Transmission
Authors: Urick R. J.
Published: September 2005

The existence and characteristics of deep convergence or focusing zones have been investigated by means of ray diagrams and field measurements using explosive charges dropped from an aricraft. The zones are found to migrate regularly with change of receiver depth, and exhibit at convergence gain of 5–10 dB for a source depth of 800 ft for the velocity profile applying for the field measurements. The pattern of the caustics that bound these zones in the deep ocean channel is a complex one, but can be roughly characterized as a series of double caustics branching out from the ray that is horizontal at the depth of the source in the ray diagrams.
Methods of Generating High-Intensity Sound with Loudspeakers for Environmental Testing of Electronic Components Subjected to Jet and Missile Engine Noise
Authors: Hilliard John K. , Fiala Walter T.
Published: September 2005

This paper discusses several methods for generating high-intensity sound in the laboratory. Typical characteristics of the two most promising methods—the plane wave tube and the reverberant box—are discussed. A simple formula for the reverberant box is derived. Measurements made on several sound generators commercially built are presented.
Elastic Strain Produced by Sudden Application of Pressure to One End of a Cylindrical Bar. I. Theory
Authors: Folk Robert , Fox George , Shook C. A. , Curtis C. W.
Published: September 2005

A double transform method is used to solve the problem of determining the elastic strain in a semi-infinite cylindrical bar with a stress free lateral surface, subject to the end conditions that the stress applied normally to the end is uniform and has a step function time dependence and that the radial displacement at the end is always zero. The exact solution appears as a sum of Fourier integrals whose integrands have the form of Pochhammer-Chree waves. These integrals cannot be evaluated in general by simple means, but asymptotic solutions have been obtained which are valid for large distances of travel. The theoretical predictions are compared with the results of experiment in a companion report.
Vibration of Axially Loaded Beams Carrying Distributed Masses
Authors: Cox Hugh L.
Published: September 2005

The lowest two natural frequencies of flexural vibration are obtained, by the use of energy methods, for uniform axially loaded beams which rest on elastic foundations and which carry masses that may be distributed symmetrically along portions of the spans of the beams. The ends of the beams may be either pinned or clamped. Simple formulas for the lowest two frequencies are given so that one may compute rapidly a desired frequency and determine the effects of the various parameters which influence that frequency.
Note on the Backscattering of Sound from the Sea Surface
Authors: LaCasce Elroy O.
Published: September 2005

Experimental observations of backscattering from the sea surface are compared with computations based on an idealized surface. The scattering at angles near normal incidence is related to the theory of scattering from a sinusoidal surface. Scattering patterns for superposed sinusoids indicate the effect of ripples on backscattering.