bluuebunny/crossref_metadata_2025 huggingface dataset:
Binaural Interaction of a Click with a Click Pair
Authors: Harris Gerard G. , Flanagan James L. , Watson Bernard J.
Published: September 2005

The binaural interaction between a single click and a click pair was examined. Two clicks with time separations of 0.5, 1, 2, 4, and 8 msec were presented to one ear, and a single click of controllable interaural time was presented to the other. Two polarity patterns (rarefaction-rarefaction vs rarefaction; and rarefaction-condensation vs rarefaction) were used at pattern rates of 2/, 10/, and 50/sec. Four subjects were asked to adjust interaural time to center all discernable sound images. Lateralizations corresponding to temporal alignment with individual clicks in the pair were found for 8-msec and sometimes for 4-msec separation. For these conditions, the subjects were consciously aware of two images. With 1-msec separation of the pair, subjects were aware of only one image, but in repeated adjustments temporally aligned at both clicks. With 2-msec separation, however, no significant lateralizations were made at the time of the second click. Only one image was discernable corresponding to lateralization of the first click. Analog basilar-membrane displacements produced by the stimuli correlate with some details of the results, but do not explain the absence of a second lateralization at the 2-msec pair separation. The neural mechanisms usually invoked to explain a minimum time interval of about 3 msec are also not adequate to explain these results. Possible explanatory mechanisms such as temporal summation and a neural gate are discussed.
Threshold Mechanism and Masking by Noise
Authors: Wansdronk C.
Published: September 2005

Some experiments are described from which we may conclude that we still cannot be sure that detection of a sound at its threshold intensity is exactly similar to detection of a sound in an external masking noise field.
Display of Sound Spectrographs in Real Time
Authors: Harris Cyril M. , Waite William M.
Published: September 2005

A technique is described for displaying sound spectrographs in real time. The patterns are obtained by scanning the rectified output of a bank of filters and feeding the output into a standard PPI oscilloscope from a radar system. Thus, no specially constructed visual display unit is required. A method of changing the frequency resolution of the patterns so obtained is described.
Comments on “Influence of Shock-Machine Loading on Shock Spectra”
Authors: Bort R. L.
Published: September 2005

Calculations recently presented have been interpreted as indicating that the maximum acceleration of a resonator mounted on a shock platform is little affected by the weight of the resonator for tests in which the initial acceleration pulse of the platform is specified. This letter points out that an important assumption of the calculations is seldom fulfilled in actual shock testing and describes alternate calculations which suggest that a resonator with mass equal to the mass of the platform may be overtested by more than 30% or undertested by more than 25% if the platform acceleration is a nominal sawtooth pulse with a specified peak terminal acceleration.
Computation of Farfield Characteristics of a Transducer from Nearfield Measurements Made in a Reflective Tank
Authors: Baker D. D. , McCormack K.
Published: September 2005

The directivity pattern and source level of a large cylindrical transducer were computed from nearfield pressure amplitude and phase measurements made under conditions simulating those in a reflective tank of diameter about 1.5 times that of the transducer. The measurements were made on the leading edge of the received pulses—before steady-state conditions were reached. This caused the pressure-amplitude data to be a few dB below the equivalent steady-state amplitudes. Computed directivity patterns agreed well with measured ones, but computed source levels were about 3 dB low. A correction term was derived from the first portion of the pulse-risetime curves and was applied to the source-level values to give good agreement with measured ones. The present results indicate that accurate transducer calibrations can be obtained in reflective tanks considerably smaller than those used in previous work.
Instrument to Measure Water-Wave Height
Authors: Crews A. A. , Erath R. L.
Published: September 2005

A simple and reliable instrument to measure the height of small water waves is described herein. The main feature of the instrument is a probe constructed of stainless-steel welding rods. Tests show that a linear electrical output can be achieved for water displacements up to 3 inches.
Comment on Errors due to Temperature and Readout Systems for Sing-Around Velocimeters
Authors: Lovett J. R.
Published: September 2005

The change of sound absorption with temperature has less effect on accuracy than do circuit-temperature changes and conventional readout systems.
Monaural Loudness Function at 1000 cps and Interaural Summation
Authors: Hellman Rhona P. , Zwislocki J.
Published: September 2005

A monaural loudness function is determined for 1000 cps and compared to a previously obtained binaural loudness function. Although the monaural function appears to have a somewhat smaller exponent than the binaural one, the empirical evidence does not permit rejection of the hypothesis of a simple interaural loudness summation. The psychophysical methods of magnitude estimation with and without a designated standard and of magnitude production without standards are used. A combination of magnitude estimation and production without standards is accepted as a method with minimum bias and classified under a more general methodological category called “psychological magnitude balance.”
Physical Dimensions of Spectrum Levels and of Spectral Densities of Acoustic Powers Energy, and Related Quantities
Authors: Baxter Lincoln
Published: September 2005

Spectrum levels should be based on spectral density measurements or estimates. The concepts of vector spectral density and two mathematical expressions for scalar spectral density are reviewed, and units of several measures of spectral density are given. The techniques and concepts appropriate for measurements of pulses are contrasted with those appropriate for measurements of continuous signals.
Nonlinear Interaction of Two Soundbeams
Authors: Lauvstad V. , Tjötta S.
Published: September 2005

An asymptotic formula is given for the sound generated by nonlinear interaction of two soundbeams of frequencies ω1 and ω2 propagating in the same direction. The formula is valid outside the primary beams, and gives the generated sound of frequency |ω1 −ω2|, provided its wavelength is large as compared with the linear dimensions of the cross section of the interaction region, and provided this interaction region is located in the Fraunhofer zones of both the primary beams.
Analysis of Rough Surfaces by Scattering
Authors: Liebermann Leonard N.
Published: September 2005

Although the general theory of scattering from rough surfaces is complicated, a simple result obtains for determining the roughness “wavelength” responsible for maximum scattering. It has been verified by a Doppler-scattering experiment that the most effective scattering “wavelength” is given by the diffraction grating formula d = λ(sinθ+sinφ)−1, where λ is the incident-radiation wavelength. In this manner, scattering provides a simple method for the analysis of surface roughness.
Dissipative Forces inside a Vibrating Magnetostrictor
Authors: Witting James M.
Published: September 2005

General expressions for forces acting on a volume element of a magnetostrictor are derived correct to first order in the ratio of energy dissipated per cycle to maximum energy stored. They are in a form suitable for setting down equations of motion.
Longitudinal Space-Time Correlation Function in Turbulent Airflow
Authors: Bakewell Henry P.
Published: September 2005

The longitudinal space-time correlation function of the fluctuating pressures at the wall in turbulent flow has been measured in the U. S. Navy Underwater Sound Laboratory'a 3.5-in. turbulent pipe-flow facility. Measurements in octave and half-octave frequency bands at zero time delay and at various spatial separations of the transducers are presented and compared with theoretical investigations to illustrate the effect of finite filter bandwidths on the longitudinal space-correlation function.
Effects of Thermal Conduction in Sonoluminescence
Authors: Hickling Robert
Published: September 2005

Current experimental results indicate that sonoluminescence is largely thermal in origin, with the spectra showing a direct relation between luminous intensity and the temperatures generated inside the collapsing cavitation bubbles. In the present paper, the strong dependence of the luminous intensity on the nature of the gas dissolved in the liquid is explained in terms of thermal conduction. Provided the cavitation bubbles are sufficiently small, loss of heat from the bubble into the liquid can significantly reduce the temperatures attained during collapse, so that there is a consequent reduction in the luminous intensity. This process is demonstrated analytically by means of a numerical solution of the equations of motion of a gas inside a collapsing cavitation bubble. The agreement between the theory and the observed luminous intensities for different dissolved gases is good.
Symmetric Planar Vibrations of a Rotating Disk
Authors: Bhuta Pravin G. , Jones John P.
Published: September 2005

The complete problem of coupled symmetric radial and torsional vibrations of a thin, rotating, circular disk has been solved, using undeformed coordinates. The formulation of the problem used here yields several interesting and previously unreported results for the static problem. Two types of instabilities occur: “static resonances” and classical instabilities, for which radial and torsional displacements everywhere in the disk can become unboundedly large. These resonances have been explained physically. The solutions of the frequency equation and the mode shapes are obtained. The effect of rotation is to lower the natural frequencies of the disk. When deformed coordinates are used, as is the case in the classical analysis of a rotating disk, the instabilities are concealed.
Response of Elastic Structures to Statistically Correlated Multiple Random Excitations
Authors: Trubert Marc R. P.
Published: September 2005

An experimental investigation pertaining to a random space-time loading, with various correlations acting on a linear elastic structure, has been carried out in an attempt to verify the validity and the feasibility of a numerical prediction of the response spectrum of the structure. The verification was made on a cantilever beam for loadings applied simultaneously at two different points on the beam while the response of the beam was measured at a third point. The structural characteristics of the beam, needed for the computation of the response, have been represented by its transfer function. The latter was determined experimentally by a cross-correlation technique using one random load at a time applied at a single point of the beam. The power spectral density of the response was computed numerically, and a computation was made with the measured power spectral density of the response for the same loading. A reasonable agreement between the two spectra was found in this comparison for nine different cases of correlated loading. Some consideration was given to the effect of the cross correlation of the input forces on the response. The response to completely correlated loadings was compared, theoretically and experimentally, to a completely uncorrelated loading showing a definite influence of the cross correlation of the input forces on the determination of the response spectra. However, the root-mean-square value of the response was found to be relatively insensitive to the cross-correlation effect.
Influence of the Time Interval on Experimentally Induced Shifts of Pitch
Authors: Christman Raymond J. , Williams William E.
Published: September 2005

Shifts in the apparent pitch of a 600-cps standard tone as a function of prolonged (60-sec) stimulation with pure tones differing in frequency from the standard tone are described. A theoretical basis for the phenomenon is suggested, and data are presented showing the results of manipulating the time interval between the satiation tone and the test stimuli. Apparent shifts on the order of 6 to 8 cps for 1-sec intervals, decreasing to 1 cps for 60-sec intervals, are demonstrated for both 575- and 635-cps satiation tones.
On (Aerodynamic) Noise Arising from the Use of Pressure Quadrupoles
Authors: Powell Alan
Published: September 2005

An objection to an analysis concerned with the use of the Laplacian of the pressure as a source term for aerodynamic noise is examined. It is shown that no useful conclusion can be drawn from the development of the objection. More-recent work confirms that serious error may result unless due care is exercised.
Coupling Cements for Ultrasonic-Wave Velocity Measurements at High Temperatures
Authors: Fisher E. S. , Renken C. J.
Published: September 2005

Two cements have been found for propagating ultrasonic compressional and shear waves into small metal single crystals from a fused silica buffer rod at high temperatures in vacuum. A quasiwater glass cement composed of sodium silicate solution, sodium metasilicate powder, and calcium carbonate has been used for elastic constant measurements with zirconium and titanium single crystals up to 883°C. An epoxy phenolic resin has been used for a similar purpose with uranium up to 610°C for compressional waves and 350°C for shear waves. The optimum conditions for use of the cements are described. The elastic constant data are not included.
Simplified Analysis of the Rijke Phenomenon
Authors: Maling George C.
Published: September 2005

The wave equation including source terms that arise because of introduction of heat into a medium has been used as the starting point for a small-signal analysis of the Rijke phenomenon. The dependence of the onset of oscillation on mean flow velocity through the tube has been found for three different values of heater power. The results of the analysis compare favorably with experimental results when the cutoff occurs at high flow velocities. At lower flow velocities, the analysis is not satisfactory because of an instability in the mean flow.
Remarks on a Paper by Jones and Kobett
Authors: Waldow Peter , Rollins Fred R.
Published: September 2005

It is proposed that the classical treatment that predicts the generation of a scattered wave of frequency (ω1 −ω2) as the result of the interaction of two plane elastic waves of frequencies ω1 and ω2 has its quantum mechanical analogy if a phonon-“splitting” process is considered.
On Sound Radiation in Terms of Pressure Independent of the Sound Speed
Authors: Powell Alan
Published: September 2005

The surface integrals of the solution to the homogeneous wave equation are discussed with special reference to the use of the pressure independent of the sound speed and point multipole representation for small surfaces enclosing the source. It is shown how the multipole representation can be used for not small surfaces, so as to afford simplification in estimating such pressures, even though the series of multipoles may diverge. The corresponding use of such pressures in the inhomogeneous wave equation is examined. The general solution for surfaces of arbitrary size contains both the aforementioned surface integrals and a volume integral over the region interior to that closed surface. The former stands alone for small surfaces and closely represents real physical conditions. The volume integral may stand alone, provided that the net monopole strength is zero and that the region of integration extends far enough for the retained time-delay effects to cause the volume integral to converge. The volume integral has the mathematical interpretation of repairing the deficiency of the surface integrals when the fictitious pressure is used in them, and consequently is unconnected with the actual basic mechanism of the source. The mathematical discussion is supported and illustrated by direct use of monopole, dipole, and lateral quadrupole fields.
Equalization and Cancellation Theory of Binaural Masking-Level Differences
Authors: Durlach N. I.
Published: September 2005

In this paper, a quantitative “black-box” model is developed for use in interpreting certain data on binaural-masking-level differences. The basic idea of this model is that the auditory system attempts to eliminate the masking components by first transforming the stimuli presented to the two ears so as to equalize the two masking components, and then subtracting. In order to obtain results that are quantitatively realistic, this processing is assumed to be corrupted by various types of errors. The model is applied to data in which the signal to be detected consists of a pulsed tone, the masking signal consists of loud, broad-band, Gaussian noise, and the only differences between the stimuli presented to the two ears are those of time delay or amplitude (the interaural amplitude ratios being restricted to unity or zero). The results indicate that the ability of the auditory. system to control interaural intensity ratios and interaural time delays is limited to accuracies of about 1 dB and 150 μsec and that the auditory system has difficulty in compensating for interaural time delays greater than the time it takes for sound to travel a distance equal to the width of the head.
Responses to Acoustic Stimuli from Single Units in the Eighth Nerve of the Bullfrog
Authors: Frishkopf Lawrence S. , Goldstein Moise H.
Published: September 2005

Single unit recordings from the eighth nerve of the bullfrog reveal two strikingly different kinds of auditory units. Both kinds of units exhibit sharply frequency dependent sensitivity (tuning curves). “Simple” units are maximally sensitive to tone bursts of frequency between 1000 and 1500 cps. Their frequency sensitivity and their capacity to “follow” pulse stimuli are well-matched to the spectral composition and pitch period, respectively, of the bullfrog's croak. Simple units cannot be inhibited by acoustic stimuli. “Complex” units are inhibited by acoustic signals in the frequency range from 300 to 1000 cps. Some complex units are excited by acoustic stimuli, some are excited by both acoustic and vibratory stimuli, and some are excited by vibratory stimuli alone. Complex units that can be excited by sound are most sensitive to frequencies between 200 and 700 cps. Simple and complex units probably derive from separate sense organs (the basilar and amphibian papillae, respectively) within the otic capsule. There is evidence that all of these responses are from primary neurons; moreover, it has been shown that the inhibition is not under efferent control. Extremely sensitive units of both types are found with thresholds comparable to those of human listeners. Responses to tone bursts, noise bursts, click trains, and frog croaks are compared. The roles of spectral and temporal pattern of the stimulus in determining the response of a unit are explored.
Pitch-Synchronous Time-Domain Estimation of Formant Frequencies and Bandwidths
Authors: Pinson Elliot N.
Published: September 2005

A technique for the measurement of vocal-tract formant frequencies and bandwidths during voiced speech is described. A theoretical justification for the method is presented, based on a model of the vocal tract that is linear and stationary over time intervals of the order of one pitch period (approximately 0.01 sec). In brief, the technique consists of selecting a portion of one pitch period of a speech waveform during which the glottis is closed. This finite-duration signal is approximated in a weighted-least-squares sense by a function of the form f̂(t) =  ∑ i−1Ne−πBit(ai cos2πFit+ci sin2πFit)+a0, where ai, ci, Fi, and Bi are selected to minimize the weighted-squared error between f̂(t) and the actual speech signal of interest, f(t). Bi and Fi are estimates of the bandwidth and frequency, respectively, of the ith formant. A digital-computer program was used to perform the minimization. The program was used to determine the bandwidths and frequencies of the first four formants of the vowels /i/, /ɔ/, and /ɑ/ in the context b(vowel)t. Two male speakers produced most of the speech waveforms. The technique seems to be most reliable for the first two formants. It yields results that appear to have a smaller variance than those obtained by previously reported methods, although the variance is still substantial.
Degradation of DNA by Intense, Noncavitating Ultrasound
Authors: Hawley S. A. , Macleod R. M. , Dunn F.
Published: September 2005

Previous research leads to the conclusion that intense, noncavitating ultrasound affects tissue at the level of macromolecular structures. As an initial study of the interaction of intense sound waves and macromolecules, solutions of DNA were irradiated with noncavitating, 1-Mc/sec ultrasound at intensities in the neighborhood of 30 W/cm2. Sedimentation-velocity analysis shows that the molecular weight of the DNA is reduced. Cavitation and thermal processes can be eliminated as possible degradation mechanisms. It is suggested that relative motion between the macromolecules and the suspending medium may be the mechanism by which degradation occurs.
Reflection of a Plane Sound Wave from a Sinusodial Surface
Authors: Uretsky Jack L.
Published: September 2005

Reflection coefficients have been computed, on the basis of an exact formulation, for the reflection of a plane sound wave from a sinusoidal pressure-release surface. Comparison with experiment and some approximate formulations is given.
Force on and Motion of a Spherical Obstacle in a Spherical Sound Field
Authors: Wasel A. D.
Published: September 2005

In the past it has been deemed of interest to study the problem of determining the force, averaged over time, exerted by a spherical sound field on a rigid sphere, opaque to the field and free to move in the field. It seems equally of interest to consider the dynamics of motion of such a sphere under the action of the sound field. The objective of this note is to show the calculation of the instantaneous force due to the sound pressure acting on the sphere integrated over the surface, allowing for the motion of the sphere. The equation of motion of the sphere is set forth, and it is noted that methods of determination of a numerical solution of equations of this form are well known.
Formant-Frequency Extraction by the Method of Moment Calculations
Authors: Suzuki Jouji , Kadokawa Yasuo , Nakata Kazuo
Published: September 2005

The method of moment calculation was used for formant-frequency extraction in computer processing from a digitalized spectrum pattern. Special attention was paid to the separation of frequency range for each formant. F̄, the first-order moment of speech power spectrum, and F2e, the ratio of the second-order moment to the first one of the spectrum, are used in this separation. Formants are calculated as first-order moments within the separated portion of the spectrum. Analyses of errors of extracted formant frequencies due to the various factors such as the increase of pitch frequency, etc., were carried out by using the synthesized vowel-type spectra simulated on the computer. This analysis and comparisons of extracted formant frequencies from the natural speech with the corresponding spectrograms have proven that the method gives acceptable results in actual speech analysis. The results can be regarded as first approximation of formant frequencies as bases of more detailed analysis such as “analysis-by-synthesis.”
Electrostatic Microphones with Electret Foil
Authors: Sessler G. M.
Published: September 2005

In this paper the operation of electrostatic microphones with foil electrets is studied theoretically. It is assumed that a foil electret has equal (free or bound) constant charges of opposite sign on its two surfaces. A formula is obtained which shows the generated output voltage of the microphone to be a function of the surface charges of the electret, the geometrical dimensions of the microphone, and the externally connected resistance. According to this formula, typical sensitivities of a few mV/μbar can be expected.

The electret microphone is also compared theoretically to a similar system with nonelectret foil. The calculations show that a surface charge of 10−8 C/cm2 on the surface of 12-mil Mylar foil corresponds to a bias of about 45 V in the nonelectret reference system. It is pointed out in this connection that the measurement of surface charges of foil electrets by the induction method requires a correction formula.
Ultrasonic Atomization of Liquids
Authors: Peskin Richard L. , Raco Roland J.
Published: September 2005

A theory of ultrasonic atomization of liquid films is presented. It is assumed that exponential growth of surface disturbances ultimately results in the formation of liquid drops, the diameters of which are proportional to the wavelength of the most rapidly growing initial disturbance. The hydrodynamic stability equations of the liquid film are examined, and the most rapidly growing initial disturbances are determined by numerical solution in the unstable region. A resultant correlation between drop size, transducer frequency, transducer amplitude, and liquid-film thickness is obtained. Results are compared to previous theoretical and experimental conclusions.
Effect of Lack of Parallelism of Sample Faces on the Measurement of Ultrasonic Attenuation
Authors: Truell Rohn , Oates William
Published: September 2005

The measurement of ultrasonic attenuation and velocity at megacycle frequencies demands that the sample faces be parallel within limits that require extreme care. The importance of maintaining the tolerances in question is shown in terms of the echo patterns for various cases in which the tolerances are held and in which they are not. In order to measure attenuation of crystalline quartz to within about 10% at 1000 Mc/sec, the required wedge angle θ should be about 5×10−8 rad or less. This turns out to be just barely possible. under rather special conditions. At the highest frequencies attained thus far (i.e., about 25 000 Mc/sec) with ultrasonic stress waves, the limits on parallelism are so severe that there are at present no instruments capable of making the necessary measurements to control the sample parallelism.
Effect of the Nearfield on the Cavitation Limit of Transducers
Authors: Sherman Charles H.
Published: September 2005

The cavitation-limited acoustic power of a transducer depends on its nearfield structure. Cavitation begins when the pressure amplitude reaches a certain value, but the pressure distribution is usually not uniform, and only the pressure component in phase with the velocity contributes to radiated power. In estimating cavitation limits, these near field effects must be considered as well as those effects that depend on the properties and condition of the medium. An analysis of cavitation-limited power that clearly separates the nearfield effects from other effects is presented here. A parameter γ that determines the nearfield effect on the cavitation limit is defined, and γ is calculated for circular pistons, hemispherical pistons, flexural plates, and multipole spheres. The values of γ are usually in the range 0.25–1.0, where unity corresponds to no near-field effect, and a value less than unity means that the cavitation-limited power per unit area is reduced by that factor.
Analysis of Reflection Patterns in Auditoria
Authors: Lochner J. P. A. , Meffert P.
Published: September 2005

Recent investigations in this laboratory made it possible to compute the intelligibility of speech from reflection patterns in auditoria. The present paper describes how standard laboratory equipment could be used for analyzing the reflection patterns into a form suitable for computation.
Sensory Thresholds and Response Bias
Authors: Norman Donald A.
Published: September 2005

Sensory differential thresholds are studied by two models: a discrete model, the neural quantum theory, and a continuous model, signal detectability theory. A comprehensive series of auditory experiments is reported that was designed to obtain measures of both the detection and decision processes of the observers when the signal consists of a brief increment in the amplitude of a pure 1000-cps tone. The analyses performed on these experiments support the existence of a low differential threshold in hearing. These analyses include the location of the isosensitivity functions and the characteristics of the psychometric functions. The experiments do not, however, provide sufficient evidence to permit a definite conclusion about the validity of the neutral quantum theory, except that it is clear that the decision model applied to the quantum theory is incorrect for “high”-amplitude signals.
Some Experiments in Unsteady Aerodynamics Leading to the Development of an Acoustic Drag Coefficient
Authors: Rubin E. S. , Kerwin E. M.
Published: September 2005

In the course of some supersonic wind-tunnel experiments, an unsteady flow condition was encountered. A significant increase in drag accompanied the instability. It has been possible to account approximately for the drag increase by means of an acoustic drag coefficient based on the acoustic power withdrawn from the flow. The experiments were carried out at Mach numbers 3.5 and 4.3 for a cylindrical model, closed at its ends, with a flow-separation spike extending from the upstream end. Several steady and unsteady flow regimes were observed. For spike lengths of about 2-cylinder diameters a stable conical shock was attached at the spike shoulder. For somewhat shorter lengths, however, a strong oscillation of the shock took place, accompanied by a pronounced increase in drag. A simplified, one-dimensional model is treated analytically, and an expression for the acoustic disturbance downstream of an unsteady shock is developed. (Some differences from published work are noted.) On the basis of this expression the acoustic power radiated by the oscillating shock is estimated. The energy removed from the flow as acoustic power represents work done on the model by the flow. Thus an acoustic drag coefficient can be specified, which is found to account approximately for the observed increase in drag.
Summating Potential of the Cochlea in the Guinea Pig
Authors: Konishi Teruzo , Yasuno Tomohiro
Published: September 2005

The cochlear microphonics and the summating potential were recorded simultaneously by means of a superfine micropipette which was introduced into scala media through the round window. A sudden jump in dc resting potential from negative to positive occurred as the tip of the electrode penetrated the reticular lamina. At this instant a reversal in polarity of the summating potential and the cochlear microphonics was observed. The polarity and amplitude of the summating potential to long-lasting pure tones were dependent not only on intensity and frequency of stimuli but also upon the position of the recording electrode along the cochlea. A dc polarizing current was applied between scala vestibuli and scala tympani in the basal turn. Although both the positive and negative summating potentials were usually enhanced by dc current traveling from scala vestibuli to scala tympani and depressed by the dc current in the opposite direction, there were several exceptions. This fact suggests that the hair-bearing surface of the hair cells becomes unstable when the intracellular potential is changed markedly. Inconsistency of the summating potential with respect to both magnitude and polarity may be due to the instability of the hair cells that are exposed to a high potassium environment and a continuous anodal polarization in the form of the endocochlear potential.
Aerodynamic Noise Produced by a Freely Suspended Rotating Cylinder
Authors: Nelson W. L. , Grundy A. B. , Trachtenberg A.
Published: September 2005

This paper describes measurements of noise produced at the surface of a high-speed rotor which is magnetically suspended and accelerated in a test chamber with controlled atmospheric conditions. Measurements of air drag and temperature rise at the high-speed surface also will be described. [This work has been supported under Air Force Contract No. AF-33(616)-2331.]
Frequency-Dividing Networks
Authors: Fleming Lawrence
Published: September 2005

Where two complementary filters (crossover networks) are used for frequency-band division in sound reproduction, the sum of the outputs usually contains considerable phase distortion. Subtractive arrangements using a single filter can be made free from such distortion, but have been complicated to realize in practice. A subtractive filter is described which is simple and cheap.
Origin of Mechanical Bias for Transducers
Authors: Miller Harry B.
Published: September 2005

The people who were familiar with the birth of this invention have agreed to speak for the inventor before the origin gets hopelessly forgotten.
Power Engineering Problems in Sonic Processing
Authors: Camp Leon
Published: September 2005

In the past, sonic processes operating discontinuously at levels of a few hundred watts did not require that the engineer design for optimum utilization of energy or avoid apparatus subject to rapid deterioration through fatigue. This paper discusses some of the problems introduced by the use of continuous power levels of hundreds of kilowatts.
Effect of Cutoff Configuration on Pure Tones Generated by Small Centrifugal Blowers
Authors: Lyons L. A. , Platter S.
Published: September 2005

Two methods for reducing the blade-passage tone of a centrifugal blower are presented, and their effectiveness is described.
On Transonic Pressure Fluctuations
Authors: Franken Peter A.
Published: September 2005

Data on transonic pressure fluctuations are related qualitatively to the corresponding local flow conditions.
Sabine Reverberation Equation and Sound Power Calculations
Authors: Young Robert W.
Published: September 2005

Three reverberation time equations and three sound power equations are scrutinized for their utility in the calculation of sound power from measurements of the average steady-state sound pressure level and reverberation time in a reverberant room. It is noted that the Sabine reverberation time equation is theoretically plausible for this use, even in a moderately absorbing room, providing it can be established that the average sound energy density decays exponentially with time. The sound power calculation may also be performed in terms of the “Sabine absorption” which is simply the absorption computed (by the Sabine equation) from the observed reverberation time and room volume. The “Sabine absorption coefficient” may exceed unity; indeed, it approaches infinity as the walls of the room become completely absorbing. An experiment was performed in a concrete room of volume 1350 ft3, to which three amounts of sound absorbing material were added. Under these four conditions the appropriate measurements were made with two independent systems (one having half-octave bands, the other third-octave bands), from which were calculated the sound power spectra of a printing calculator and a unit heater. In addition to simplicity, both theory and experiment support use of the “Sabine absorption” instead of the “room constant” in the calculation of sound power.
Criteria for Noise in Office Spaces
Authors: Beranek Leo L.
Published: September 2005

This paper is a report on continuing research on acceptable noise levels in office spaces. A new questionnaire has been tried with different adjectival cues and more categories on the rating scales. The results with this questionnaire show a nonlinear relation to those obtained from the previous study. The maximum permissible noise levels are in agreement with those published earlier. More difference between the stenographic and the executive personnel's requirements were obtained during this study than was the case for the previous study.
Prediction of Noise Levels in Buildings
Authors: Goodfriend Lewis S.
Published: September 2005

The prediction of noise levels in living and working spaces is of considerable importance in the architectural design of buildings. Two charts have been developed which simplify the tedious process of calculating the level of noise entering a room through walls, floor, and ceiling from both interior and exterior sources. The use of published transmission loss and sound-absorption data with the charts and some simple data forms allow the rapid estimation of interior noise levels without resort to slide rule or log tables. Accuracy is commensurate with one's ability to determine criteria for background noise in the spaces under consideration.
Prediction of Noise Reduction and Privacy in Modern Office Structures
Authors: Farrell W. R. , Watters B. G.
Published: September 2005

Because of the architectural and mechanical advantages of constructing office partitions only to the height of an acoustic tile ceiling, the problem of noise transmission above the partition and the resulting loss of privacy is occurring increasingly frequently. This paper discusses a method of predicting the noise reduction along this path in terms of the conventional room factors of the source and receiving rooms as well as factors such as the acoustic tile material and configuration, the height of the space above the ceiling, the width of the rooms, etc. A tentative method of evaluating the “degree of speech privacy” afforded by a given NR in the presence of a given background noise spectrum is also shown.
Acoustics of the Jacksonville Civic Auditorium
Authors: Klepper David L.
Published: September 2005

The new civic auditorium in Jacksonville, Florida, consists of three major spaces: 3200-seat auditorium, a 600-seat theater, and 20 000 sq ft of exhibition space. The main auditorium will accommodate a variety of speech and music activities. It has a volume of one million cu ft and a design reverberation time (full) of 1.7 sec at midfrequencies. Essential to the acoustical design is a demountable plywood stage enclosure for orchestral concerts. The paper compares the predicted reverberation times for the auditorium with measurements obtained following completion of the building. The room-acoustics design illustrates why some auditoriums require suspended sound-reflecting panels for “first reflections” under a higher surface that forms the acoustical boundary of the space, providing the necessary volume.
Some Recent Advances in Soundproof Openings
Authors: Munchhausen H. V.
Published: September 2005

While in the past it has been difficult to give structural openings a sound transmission loss of the same order as that of the walls, recent work on doors, windows, and ventilation ducts has achieved this goal. Slides will be shown of the basic design of such structures and of typical installations. Measurements at the National Bureau of Standards will be cited.
Exposure to Steady-State Noise and Impairment of Hearing
Authors: Kryter Karl D.
Published: September 2005

A damage risk criterion for exposure to noise is specified primarily in terms of the impairment of speech communication as the result of noise-induced deafness. The criterion allows as permissible any noise exposure that, on the average, causes a temporary threshold shift measured 2 min after exposure, in the average normal ear, of no more than 10 dB at 1000 cps or below; 15 dB at 2000 cps; or 20 dB at 3000 cps or above. It is held that after 10 years of near daily exposure to such a noise, the average person will have a stable hearing level, relative to present-day audiometric zero, of a similar magnitude. To determine what kinds of sounds and durations of exposure would meet this criterion, twelve ears were exposed to bands of filtered, random noise for durations ranging from 3 min to 8 h. Temporary threshold shifts for pure tones were obtained by comparing pre- and post-exposure audiograms. From these data functions were obtained which show the sound-pressure level, durations, bandwidth, and center frequency of bands of noise that cause, on the average, temporary auditory fatigue equal to the maximum allowed by the aforementioned criterion. The critical bandwidth for noise with respect to auditory fatigue appears to be slightly wider than 13 octave for the frequency region covered in these tests.
Printing Machinery Isolation
Authors: Miller Laymon N. , Dyer Ira
Published: September 2005

An engineering office is located beneath a printing shop in a particular all-concrete industrial building. The engineers in the office have complained about the high noise levels caused by the printing machines, most of which were mounted directly on the concrete floor overhead or on wood skids. This problem led to the design and evaluation of vibration isolation pads for a representative printing press such that the noise levels in the engineering office may be reduced to reasonable acceptable values. This paper summarizes pertinent airborne and structure-borne noise levels before and after installation of the vibration mounting arrangements for one printing press.
Use of the Aural Reflex to Measure Ear-Protector Attenuation in High-Level Sound
Authors: Nixon C. W. , Sommer H. C. , Cashin J. L.
Published: September 2005

A technique of tympanomanometry developed for study of the aural reflex was adapted for use as an objective psychophysiological method for measuring attenuation of ear protectors in high-level sound. Four representative ear protectors (an insert, a semi-insert, a small-volume muff, and a large-volume muff) were evaluated by this aural-reflex method and by ASA REAT method. Attenuation was designated in both instances as the mean difference between threshold values with and without ear protection (threshold shift). The aural reflex with ear protection was measured only for frequencies ranging from 400 to 4000 cps due to limitations of the signal source. A comparison of the results shows that, for the frequency range used, the aural-reflex threshold-shift method gives attenuation data comparing favorably with other above threshold data. The absolute-detection threshold-shift method indicates somewhat greater attenuation than does the aural-reflex threshold shift, the differences varying both with the type of ear protector and as a function of frequency. The results suggest that a single-value correction factor for adjusting standard threshold-shift attenuation data to estimate attenuation in high-level sound may not be appropriate.
Reciprocity Couplers without Effects of Wave Motion to 10 kc/sec
Authors: Embleton T. F. W.
Published: September 2005

An experimental study has shown that reciprocity couplers having the cross-sectional shape of certain irregular polygons are superior to those of circular cross section. The upper limit of microphone calibration (for type L standard microphones) without correction for wave motion in a circular cavity is about 6 kc/sec. In a cyclic pentagonal cavity having sides of 1.02, 0.61, 0.89, 0.42, and 0.75 in., respectively, and between 0.06 and 0.1 in. thick, the effects of wave motion are less than ±0.2 dB up to 10 kc/sec. Polygons of 3, 4, 5, and 6 sides were investigated, but it appears that a pentagon represents the optimum compromise between several conflicting requirements to be satisfied by the design of the cavity.
In Search of the Bone-Conduction Threshold in a Free Sound Field
Authors: ZwislocKi J.
Published: September 2005

Several investigators have attempted indirect determination of the bone-conduction threshold in a free sound field. It has recently become possible to decrease the intensity of sound transmitted through the auditory meatus to a level below that of a sound reaching the ear through other pathways. By varying the properties of sound-attenuating devices, and with the help of resonance phenomena, it could be shown that the remaining hearing was actually controlled by body conduction, if not more specifically by bone conduction. According to these measurements, the “minimum audible field” for body conduction (MAFB) exceeds 80 db re 0.0002 dyne/cm2 at low frequencies and decreases gradually to a minimum of about 45 to 50 db between 1500 and 2000 cps. For higher frequencies it increases somewhat again. The difference between body conduction and air conduction seems to be maximal in the vicinity of 500 cps, amounting to approximately 65 db. At frequencies around 100 cps the difference is of the order of 50 db. This difference holds also for the frequency range between 2000 and 6000 cps. Between 1500 and 2000 cps the difference goes down to about 45 db.
Velocity of Sound in a Dow Corning 200 Fluid as a Function of Temperature and Pressure
Authors: Bradley David L.
Published: September 2005

The velocity of sound was measured in a sample of 0.65 centistoke Dow Corning 200 Fluid. The measurements were made in an ultrasonic velocimeter, utilizing a pulse technique at a frequency of 5 Me/sec. The method of analyzing the data is given together with tables and graphs.
Hearing Acuity of Air Force Flight-Line Personnel: a Preliminary Report
Authors: Kopra Lensart L.
Published: September 2005

Pure-tone audiometric tests and job-, noise-, and medical-history questionnaires were administered to 599 Bergstrom Air Force Base flight-line personnel. Hearing loss at 4000 cps, total hours of exposure to high-level on-the-job noise, and age were analyzed to determine the inter-relationships between these three variables. At 4000 cps (worse ear) the observed mean hearing losses in eight Air Force Specialty groups ranged from 14.8 db to 20.6 db re audiometer zero. No statistically significant differences were found between group hearing-loss means when adjustment was made for differences in age and noise exposure. The interrelationships between hearing loss, age, and noise exposure were similar from one Air Force Specialty group to another. Hearing loss at 4000 cps and age were positively correlated. Age and noise exposure were positively correlated with hearing loss and noise exposure. The partial correlation coefficient between hearing loss and age differed significantly from zero. However, the partial correlation coefficient between hearing loss at 4000 cps and noise exposure was not statistically significant. These results are evidence that an extremely complex relationship exists between noise-induced hearing loss and age plus total exposure to high-level intermittent continuous noise. [This study was supported by funds provided under contract AF 41(657)-35 with the School of Aviation Medicine, U. S. Air Force, Randolph Air Force Base, Texas.]
Modulated Airstream Loudspeaker
Authors: Salmon V. , Burgess J. C.
Published: September 2005

A small amount of control energy may be used to modulate the flow of an airstream of much larger energy content, thus making possible a large acoustic output from a small modulator. Following a study of the theory of the modulation process, an improved modulated airstream loudspeaker for use in speech systems was developed, constructed and tested. It features simplicity of construction and adjustment; freedom from fouling by water, dirt, and oil; and high output in the speech range. For class A modulation (having a maximum possible sine-wave pneumoacoustic efficiency of 50%), the following performance was finally achieved: control power, 10 available audio watts; airstream power, 700 pneumatic watts; and sound output, up to 100 acoustic watts through a 0.7-in. diam throat. With a horn having a directivity index of 10 db, the 30-ft axial sound-pressure level was 122 dbp. [This study was supported by the Signal Corps Engineering Laboratories under Contract DA-36-039sc-52667.]