bluuebunny/crossref_metadata_2025 huggingface dataset:
Design and Construction of a Soundproofed Diesel Generator Power Plant
Authors: Hirschorn Martin , Schiesser A.
Published: September 2005

The original design concept of a soundproofed power plant will be described including structural vibration and airborne noise considerations. The acoustical design criteria will be presented as well as acoustic measurements after completion of power plant. The plant was designed for four 1440 hp Diesel engines, though only three are presently installed. Over-all sound level measurements of the engines were of the order of magnitude of 120 decibels. The resultant noise level immediately outside the wall of the finished power plant was less than 50 db. The plant was designed for General Motors Overseas Operations and was erected in Sao Paulo, Brazil.
Noise Estimates of a Family of Transport Aircraft
Authors: Shattuck Russell D. , Boak Roger
Published: September 2005

A series of transport aircraft having maximum gross take-off weights of 50 to 150 thousand pounds are studied to predict noise levels and the extent of disturbed areas. Propeller and turbo-jet power plants are compared.
Elastic Cylinder with Free Lateral Surface and Mixed Time-Dependent End Conditions
Authors: DeVault G. P. , Curtis C. W.
Published: September 2005

A method is described for formulating an exact solution to any problem involving an elastic cylindrical bar with a free lateral surface and mixed time-dependent end conditions. To illustrate the method and to test the practicality of simulating pure end conditions by conditions given in mixed form, a solution is obtained for a particular problem involving both longitudinal and flexural strain. Asymptotic expressions valid at large distances from the end of the bar or for long times after the load is applied are developed for the integrals of the exact solution to the particular problem and predictions based on these expressions are compared with results of an experimental test in which pure end conditions were used. In this case and for large distances or long times, all of the main features of the observed behavior were correctly predicted.
Axially Symmetric Waves in Finite, Elastic Rods
Authors: McNiven H. D. , Perry D. C.
Published: September 2005

An approximate theory of symmetric vibrations of elastic rods is used to develop frequency equations governing the vibrations of finite rods. The roots of these equations are used to form frequency spectra that predict the lower resonant frequencies of axially symmetric motions of a circular, elastic rod of given length.
Modulated Photoelectric Measurement of Vibration
Authors: Schmidt V. A. , Edelman S. , Smith E. R. , Pierce E. T.
Published: September 2005

This paper describes an improvement in the method of setting vibration amplitudes for calibrating vibration pickups by the disappearance of an interferometric fringe pattern. In the usual method, one plate of an interferometer is stationary, the other vibrates with the pickup, and the fringe pattern disappears at zeros of the Bessel function J0[(4πξ)/λ], where ξ is the amplitude of vibration and λ is the wavelength of light used. In the improved method, the fringes are observed by a photomultiplier, the previously stationary plate is vibrated at a modulating frequency much lower than the calibrating frequency applied to the pickup, and the signal from the photomultiplier, filtered at the modulating frequency, has minima at the zeros of J0[(4πξ/λ]. Observation of the nulls on a meter allows faster calibration with greater precision and less observer fatigue.
Axisymmetric Vibrations of a Conical Shell Supporting a Mass
Authors: Holmes W. T.
Published: September 2005

An analytical method is presented for determining the natural frequencies for the axisymmetric vibrations of a truncated, circular, conical shell supporting a mass fastened to its small end.
Incidence and Prevention of Damage Due to Mechanical Shock
Authors: Parfitt G. G. , Snowdon J. C.
Published: September 2005

In order to evaluate the performance of shock mountings in a simple manner, it is very desirable to express by a single quantity the liability to damage of the contents of fragile equipment. The conditions on shock duration under which the acceleration, displacement, or velocity associated with the input transient may be employed to describe the liability to damage in place of the full shock spectrum are therefore discussed.

In shock-mounted equipment it often appears desirable to avoid mechanical elements that, by virtue of their low resonant frequencies, are sensitive to changes in displacement or velocity. If this is possible, acceleration remains as the factor of chief concern, and a mount must be chosen to provide an acceptable compromise between the resulting reduction in acceleration and the introduction of relative motion. Characteristic curves facilitating this choice are proposed, and the influence of mount nonlinearity and damping on the curves is briefly discussed.
Correlation Properties of Flexural Waves in Long Thin Bars
Authors: Winter Earl F. , Bies David Alan
Published: September 2005

The correlation properties of dispersively propagating flexural waves traveling on long thin bars have been studied experimentally. The cases of a traveling wave with no reflections, with one reflection, and with many reflections have been investigated. It is shown that dispersion considerably complicates the interpretation of the cross-correlation function. The nature of the complications and the extent to which progress has been made in the interpretation of results is described.
Loudness as a Function of Signal Duration
Authors: Small Arnold M. , Brandt John F. , Cox Phillip G.
Published: September 2005

Subjects were asked to change the level of a short noise burst in order to make it equally as loud as a standard 500-msec burst. Above some critical duration loudness is independent of duration but below it for each decade decrease in duration the level of the short burst must be increased about 12.5 db, independent of the level at which the standard burst is presented.
Radiation from Unbaffled Bodies of Arbitrary Shape at Low Frequencies
Authors: Strasberg M.
Published: September 2005

A simple relation is discussed for calculating the sound pressure in the distant radiation held of an unbaffled body of arbitrary shape vibrating in an arbitrary pattern. Comparison with more exact calculations for spheroids indicates that the relation is limited to low frequencies, where the wavelength is at least 10 times the major dimension of the body.
Effect of Correlated Phase Fluctuation on Array Performance
Authors: Berman Helen G. , Berman Alan
Published: September 2005

The response of a uniform array of point detectors receiving cw signals is computed under the assumption that there are correlations in the fluctuations of the phase of the signals. General formulas are developed for various ranges of correlation. It is shown that the peak response of an array is not appreciably reduced until the magnitude of the fluctuations becomes large. If the fluctuations are strongly correlated over many receiving elements, then the main lobe will be broadened.
Responses of the Auditory Nerve to Repetitive Acoustic Stimuli
Authors: Peake W. T. , Goldstein M. H. , Kiang N. Y.-S.
Published: September 2005

Auditory nerve responses to short bursts of acoustic noise have been recorded by gross electrodes. For moderate stimulus intensities the amplitude of the response is independent of burst repetition rate for rates below approximately 10/sec. The curve of response amplitude vs rate then decreases except for a small “bump” in the curve near 600/sec. Synchronized responses were detected for repetition rates as high as 3000/sec by an average response computer. These data have been considered in terms of a model that accounts for the overlapping of the response waveforms. In terms of this model, the neural activity decreases monotonically with increasing rate above the rate 10/sec.
Pure-Tone Loudness Relations
Authors: Lochner J. P. A. , Burger J. F.
Published: September 2005

A knowledge of pure tone loudness relations is of fundamental interest to all workers in the field of human hearing. Of these relations the pure tone equal-loudness contours, three sets of which have been independently established, are probably the best known. These three sets of contours have the same general shape but show considerable deviations over parts of the auditory diagram.

Making use of the results obtained by different workers and assuming a recently established loudness-stimulus relation to hold at all frequencies in the audio range, a new set of equal loudness contours has been calculated. A set of curves giving the loudness of equal stimulus contours has also been calculated.
Design of High-Pressure Blowoff Silencers
Authors: Sparks Cecil R.
Published: September 2005

The problems associated with designing effective silencers for suppressing noise from high-pressure gas blowoffs differ somewhat from those associated with jet aircraft noise suppression because of the high expansion experienced by the gas as it is reduced to atmospheric pressure. Using a combination of aerodynamic and acoustic theory it is possible to calculate the flowing conditions which exist in a silencer and then to correlate these with noise regeneration at the silencer exhaust. Similarly, the effects of silencer internals on attenuating noise introduced into the vessel can be approximated on the basis of field tests and acoustic theory for a wide range of operating parameters. Using the techniques discussed in this paper, both the noise transmitted through a silencer and that regenerated at its exhaust can be approximated, and the over-all noise reduction characteristics of a silencer design can thereby be anticipated through the use of the analytical techniques or design charts presented.
Analysis of the Pulse Superposition Method for Measuring Ultrasonic Wave Velocities as a Function of Temperature and Pressure
Authors: McSkimin H. J. , Andreatch P.
Published: September 2005

A pulse superposition method of determining ultrasonic wave velocities in materials such as single crystals is shown to be well suited to measurements for pressure and temperature variations. With this method the effect of coupling between transducer and specimen can be made negligibly small. Data are presented for longitudinal waves propagated in the X direction of quartz and for XY shear waves propagated in the Y direction of quartz. Pressure was varied from 1 atm to 30 000 psi at 25° and −195.8°C. Curves for facilitating the measurement of absolute velocities for a range of specimen impedances are shown in the Appendix.
Range Dependence of Acoustic Fluctuations in a Randomly Inhomogeneous Medium
Authors: Stone Robert G. , Mintzer David
Published: September 2005

Measurements have been made to relate the acoustic fluctuations, resulting when a series of uniform sound pulses is transmitted through a medium in which there are random variations in space and time of the index of refraction, to the range from source to receiver, the acoustic frequency, and the parameters of the scattering medium. This paper considers the range dependence of the coefficient of variation (which is a measure of the acoustic fluctuations). A tank of water is heated from below causing the warmer, less dense, layers of water to rise by convection. This produces a medium of almost homogeneous turbulence with time and space variations in the temperature microstructure. Experimental results are in good agreement with a theory developed by Mintzer [J. Acoust. Soc. Am. 25, 922 (1953)] which predicts that the coefficient of variation of the acoustic pulses varies as the square root of range from source to receiver. There is some evidence that this dependence may be correct under broader conditions than are required by the theory.
Model Experiments with Acoustic van Atta Reflectors
Authors: Walther Klaus
Published: September 2005

A van Atta reflector consists of an array of radiators which are interconnected by transmission paths in such a way that the energy of an incident wave is reradiated back into the direction of arrival. Model experiments on backscattering from acoustic van Atta reflectors are reported. Airborne sound waves in the frequency range between 2.5 and 9.0 kc were used in these measurements. The acoustic van Atta array consists of 36 conical horns (aperture 112 in.) arranged on a 9×9-sq-in. flat surface. The horns are inter-connected by plastic tubing with reinforced walls. In these measurements the van Atta reflector shows a uniform backscattering over a wider range of angular orientation than the conventional corner reflector in the frequency range between 2.5 and 6.0 kc. For higher frequencies the angular coverage of the van Atta reflector under test is limited by the directivity of the horns. Some tests on an assembly of two van Atta reflectors, mounted at an angle of 60° with respect to each other, are reported. They show a more uniform angular response as compared to a cluster of corner reflectors in the frequency range from 2.5 to 5.0 kc.
Radiation Impedance on an Unbaffled Piston with a Back Enclosure
Authors: Strasberg M.
Published: September 2005

The radiation impedance on an unbaffled, rigid circular piston whose back side is surrounded by a small enclosure is deduced from published values of the impedance on oscillating oblate spheroids.
Modulation of the Frequencies of the Partials of Beams above the First by Vibration at I, as by the other Bending Forces
Authors: Miessner Benjamin F.
Published: September 2005

The discovery of the fact that the frequencies of the upper partials of a fixed free beam will be modulated by an existing vibration in the fundamental mode is recounted. It was found, for example, that the frequency of the second partial varied bicyclically in an amount determined by the amplitude of the fundamental mode of vibration.
Simplified Ray-Tracing Computations
Authors: Mooney Charles S.
Published: September 2005

Most ray-tracing schemes involve many numerical computations. At least one of these calculations can be simplified. The calculation for ray travel time through a layer of constant velocity gradient has been performed by calculating the first few terms of an infinite series. This method, in addition to being laborious, can lead to approximations. An alternate method employing log tables is suggested.
Acoustic Resonance Tube for High Pressures and Low f/p
Authors: Henderson M. C. , Donnelly G. J.
Published: September 2005

An acoustic resonance tube is described capable of operating at moderately high pressures and elevated temperatures: possibly 1000 atm and several hundred degrees centigrade. The frequency range is 500 to 15 000 cps, or correspondingly 0.5 to 15 000 cps/atm or higher, thus filling a significant experimental gap in acoustical instrumentation. The wall absorption in this tube is about 10% above the calculated classical value, and is approximately independent of molecular weight or pressure of the gas. Details of construction and operation are given, and the application of the tube to problems of relaxation at low frequency/pressure ratios is indicated.
Response of Nonlinear Structures to Random Excitation
Authors: Smith P. W.
Published: September 2005

Current procedures for predicting the response of dynamically nonlinear, resonant structures to random excitation are reviewed. Methods of analysis are summarized and limitations inherent in the methods and their application to practical structures are pointed out. The most important limitations are the neglect of nonlinear damping, and the description of the motion of a distributed structure in terms of a single mode.
Acoustic Attenuation in a Liquid Layer over a “Slow” Viscoelastic Solid
Authors: Williams A. O. , Eby R. K.
Published: September 2005

Low-frequency propagation in a uniform liquid layer over a “slow” viscoelastic bottom of infinite depth is analyzed. True absorption in the liquid layer is ignored, but the Lamé constants of the solid are allowed to be complex; that is, the corresponding compressional and transverse waves may suffer absorption. The compressional wave speed c2 in the bottom is assumed to exceed the speed c1 in the liquid, which in turn exceeds the transverse wave speed ct in the bottom. The eigenvalue equation for normal modes in the liquid layer is derived. Regardless of absorptions in the bottom, this equation yields complex values for the phase velocities of normal modes in the liquid, so that attenuation exists. Generally the real parts of these velocities are altered, relative to the Pekeris problem of liquid over liquid, as if the density of the lower material were decreased. Three special examples are displayed: (a) Attenuation over a nonabsorbing solid bottom; (b) attenuation over an absorbing bottom of Hycar rubber, used in an earlier model test of shallow-water propagation; (c) the joint effects of a transverse wave and small absorptions in the bottom for a mode far from cutoff, to show the degree of interdependence among the attenuations.
Can We Feel the Nervous Discharges of the End Organs during Vibratory Stimulation of the Skin?
Authors: von Békésy Georg
Published: September 2005

The vibratory pitch sensation is a complicated function of both the frequency and the amplitude of the vibrations, and frequency discrimination on the skin is thus inaccurate within a range of one or two octaves. Rutherford's telephone theory for pitch discrimination does not describe the pitch of vibratory sensations.
Relation of Mechanical Power of a Propeller to Radiated Power of the Resulting Acoustic Sources
Authors: Embleton T. F. W.
Published: September 2005

The strength of monopole- and dipole-type circular acoustic sources is related to the torque and thrust of a propeller. The power radiated in the two acoustic fields is given in terms of the same two mechanical parameters.
Shallow-Water Transmission
Authors: Marsh H. W. , Schulkin M.
Published: September 2005

Expressions and tables are presented for computing the shallow-water transmission loss as a function of bottom type, sea state, frequency. water depth, and range. A table of probable errors is also presented as a function of frequency and range.
Extrapolation of the Equation for the Speed of Sound in Sea Water
Authors: Wilson Wayne D.
Published: September 2005

The equation for the speed of sound in sea water was used to compute sound speeds at temperatures, pressures, and salinities which occur outside the range of variables in which the equation was derived. These computed values were compared with actual measured values at the same conditions to determine what errors the equation introduced.
Experimental Tunnel-Diode Electromechanical Transducer Elements and Their Use in Tunnel-Diode Microphones
Authors: Rogers Edward S.
Published: September 2005

A tunnel-diode transducer element is described in which stress is applied normal to the diode junction by a small probe. Static measurements on these elements have yielded strain gauge factors as high as 7300. A number of experimental microphones have been built to evaluate the transducers. Response frequency characteristics and S/N ratios have been determined for several of these microphones. The most sensitive microphone had a sensitivity of −31 dBm and a S/N of 45 dB at resonance. These microphones have been operated both as variable resistance transducers and as modulated negative resistance oscillator transducers. A description and analysis is given of these two basic circuit configurations. In their present form tunnel-diode transducers are fragile; further effort will be required to produce a rugged, practical transducer element.
Determination of the Parameters of a Piezoelectric Transducer from the Decay of Resonant Vibrations
Authors: Redwood M.
Published: September 2005

The usual method of determining the RLC parameters of the equivalent circuit of a transducer involves the measurement of admittance or impedance over a range of frequencies near resonance. An alternative method is described here. The transducer is first excited in mechanical resonance by applying an electrical signal; the excitation is then removed and the electrical signal produced by the transducer as the mechanical vibrations decay is observed by using an oscilloscope. Under certain conditions the parameters of the transducer equivalent circuit may be determined rapidly from measurements of the initial amplitude of the electrical signal and the rate at which it decays.

The theory of the method is described and used to determine its limitations; the method is particularly suited to rapid measurements on transducers of reasonably low coupling coefficient (less than about 0.4) and reasonably large Q (100 or more). A simple experimental system suitable for measurements to an accuracy of ±10% is discussed and investigations on a barium titanate transducer resonating in a bar mode are described in some detail; the parameters obtained using the decay method compare favorably with those obtained using the conventional admittance method.
Three-Sound-Pressures Theorem, and Its Application, in Aerodynamically Generated Sound
Authors: Powell Alan
Published: September 2005

A theorem is presented which is a direct consequence of Lighthill's theory of aerodynamic noise generation when expressed in the equivalent point-source approximation. It states that the sum of the sound pressures at points located at equal distances on each of three mutually perpendicular axes, with the origin in the flow, is zero. This is based on the incompressible-flow approximation and applies to a free flow which is inviscid and unconvected. The next approximation is given also, the sum varying as the Mach number raised to the fourth power. There is also an analogous form of the theorem for two-dimensional systems concerning the sum of the sound pressure on any two mutually perpendicular axes. The value of the theorem is demonstrated by showing how, for example, there can be, in general, no net longitudinal quadrupole strength for an inviscid noise-generating flow. This is illustrated by application to the sound radiators of a plane shear layer undergoing a two-dimensional disturbance.
Learning to Identify Nonverbal Sounds: An Application of a Computer as a Teaching Machine
Authors: Swets John A. , Millman Susan H. , Fletcher William E. , Green David M.
Published: September 2005

The procedures of automated instruction—continual interrogation and overt response, immediate knowledge of results, presentation of successive items conditional upon previous performance, learner-controlled pacing of the lesson, and so forth—were applied to the task of learning to identify multidimensional, nonverbal sounds. These procedures produced results that are comparable to those obtained previously with conventional training methods. Certain of the central features of automated instruction were found to hinder learning in the task studied.
Contributions to a Theory of Separability of the Vector Wave Equation of Elasticity for Inhomogeneous Media
Authors: Hook Joseph F.
Published: September 2005

In a recent paper, the author introduced a generalization of the Helmholtz theorem for representation of vectors in terms of potential functions. It was shown that use of this generalization leads to separation (in the dependent variables) of the vector wave equation of elasticity for certain inhomogeneous media whose properties are functions of the Cartesian coordinate s. The conditions for separability are a system of nonlinear differential equations for the constitutive parameters. Only a few special solutions of this system were given. An almost complete catalog of the separable cases is developed in the present paper.

The vector differential properties of the field for the separable cases are discussed. It is shown that the P and S fields are irrotational and solenoidal, respectively, provided we regard as the fundamental field vectors the quantities f1uP, f2uSV, and uSH rather than the displacement vectors themselves, where f1 and f2 are appropriate weighting functions. The vector differential properties of the displacement vectors themselves are derived and these results compared with similar results obtained by the eikonal method of analysis.
Calculations of Convergent Zones in a Sound Channel
Authors: Goodman R. R. , Duykers L. R. B.
Published: September 2005

A simple approximate solution for ray paths near a sound channel with parabolic velocity profile is given for rays crossing the sound channel axis at small angles. The convergent zone for such rays for a source on axis is compared with results of Pederson. Two simple straight-line-velocity gradient approximations are compared with the parabolic case for the purpose of observing their accuracy in the prediction of convergent zones. Both cases show surprisingly good agreement over a range of choices for the gradients.
Space-Time Correlation in Spherical and Circular Noise Fields
Authors: Jacobson Melvin J.
Published: September 2005

In many analyses of systems designed to detect and locate a signal source in a noise field, it is necessary to know the correlation of the noise at two points in the field at different times. While spatial effects have been considered in some studies, temporal effects are usually neglected. In this report, space-time correlation is considered as a function of frequency, point separation, and time difference when the noise is generated by independent noise sources located on a sphere and circle of infinite radius. Numerous results are obtained, the most important being that, in general, noise cross correlation will be very much greater for certain nonzero time differences than for a zero time difference. The effects of inserted time delay must therefore be considered for systems in which noise cross correlation may adversely affect performance.
Effect of Noise at One Ear on the Masked Threshold for Tone at the Other
Authors: Blodgett Hugh C. , Jeffress Lloyd A. , Whitworth Randolph H.
Published: September 2005

Hirsh found that when noise and signal are presented at one ear and noise alone to the other, the threshold for a tonal signal is lower than when the signal too is presented to both ears. The present study is concerned with this phenomenon as a function of the level of noise in the ear not receiving the signal, and as a function of the noise level in both ears. Findings are shown to be in agreement with Hirsh's and with predictions from a theory of masking phenomena.
Shock-Wave Transducer Calibration
Authors: Ziemer R. E. , Lambert R. F.
Published: September 2005

The use of a shuck-wave technique to obtain a frequency-response calibration of a small lead zirconate titanate transducer is described. The response curve is obtained through numerical Fourier transformation of the recorded response to a shock-wave excitation. Sources of error and agreement with other methods of calibration are discussed.
General Reciprocity Relation
Authors: Chertock George
Published: September 2005

A reciprocity relation is derived between the radiation field of a surface vibrating in an arbitrary mode with arbitrary time dependence. and the generalized force exerted on the surface in the same mode by an external source with the same time dependence.
Problem of Sound Scattered by Sound
Authors: Lauvstad V. , Tjøtta S.
Published: September 2005

The sound generated by the nonlinear interaction of two sound beams of high intensity, arranged to cross each other perpendicularly, is computed to the first order of interaction. Several of the assumptions and specializations in previous treatments of this problem, whose effects on the result it is hard to estimate, are avoided. The interaction is supposed to take place in the Fraunhofer zone of both beams.

Some results obtained are of general validity. For instance, the Doppler angles computed and measured by Ingard and Pridmore-Brown are found, without any strict specializations of the primary beams and the interaction region.

Estimates of the amplitudes of the generated pressure, governing rather wide ranges of frequencies of the primary beams, seem to agree with the previous apparently strongly differing results. This correspondence is brought forward by an amplitude factor, depending on the frequencies of the primary beams.

In the high-frequency limit, the destructive interference among the quadrupoles which give rise to the generated sound dominates the results and gives an over-all zero value of the generated pressure, in accordance with Westervelt's treatment.
Note on the Radial Deformation of a Piezoelectric, Polarized Spherical Shell with a Symmetrical Temperature Distribution
Authors: Sinha D. K.
Published: September 2005

The solution of the problem of static radial deformation of a piezoelectric spherical shell, polarized in the radial direction corresponding to uniform pressures on the inner and outer surfaces of the shell, and a given voltage difference between these surfaces, coupled with a radial distribution of temperature from the inner to the outer surface, forms the chief interest of the present note. The constitutive relations, deduced by Mindlin are taken in a form which closely resemble those of Toupin.
Structural Fatigue under Combined Random and Swept Sinusoidal Vibration
Authors: Spence H. R. , Luhrs H. N.
Published: September 2005

Combined random and swept sinusoidal vibration is used in the qualification of missile electronic equipment. The subject of this report is how structural fatigue produced by a combined excitation is related to structural fatigue produced by another combined excitation or to that produced by individually applied random or sinusoidal excitation. In particular, a method is given by which different random or combined random and sinusoidal vibration excitations can be compared. This method finds practical application in comparing vibration specifications and tests, and for the purpose of modifying vibration requirements from one type to another.

In this derivation, substitute sinusoidal vibration excitations and sweep rates are based on the response characteristics of a single resonator system, while amplitude and time relationships are based on the S-N diagram of the material under consideration. Equations and curves are given and their use illustrated by means of a numerical example.
Loss Factors of Viscoelastically Damped Beam Structures
Authors: Ungar Eric E.
Published: September 2005

General expressions are derived for the loss factors of axially uniform linear composite structures in terms of properties of the constituents. Specializations applicable to practical composites incorporating free and constrained viscoelastic components are introduced. The results are shown to be generalizations of earlier studies of coated and sandwich plates [Ross, Ungar, Kerwin, Sec. 3 of Structural Damping, ASME (1959)], and it is demonstrated that much of the abundant information available for such plates may be carried over to more complicated structures by redefinition of the structural and shear parameters.
Note on the Creation of Pitch through Binaural Interaction
Authors: Durlach N. I.
Published: September 2005

In this note, the Huggins creation of pitch stimulus is regarded as a binaural masking stimulus and the equalization and cancellation model of binaural masking level differences is applied to the creation of pitch phenomenon.
Some Effects of Unilateral Auditory Masking upon the Localization of Sound in Space
Authors: Butler R. A. , Naunton R. F.
Published: September 2005

The authors describe the methods used and results obtained in a series of experiments designed to examine the effects of unilateral auditory masking upon the apparent position of a sound in space. Listeners were asked to locate various pure-tone and complex-sound signals delivered by a concealed loudspeaker while pure tone or complex masking stimuli were delivered to one ear by means of a single headphone. The results of these experiments indicate that masking can have a strong and consistent effect in pulling the apparent source of the free-field signal toward the masked ear. The authors interpret this as evidence that binaural interaction is taking place and stress that most other methods of examining the phenomenon would fail to detect interaction between the types of stimuli used. The experimental data also indicate that intensity and frequency relations between signal and mask play a major role in determining the extent to which a masking stimulus will pull the apparent source of sound toward the masked ear; the effect is striking when the frequency spectrum of the mask covers that of the free-field signal; the effect may still be evident, however, when signal and mask have no frequency components in common. The wide range of frequency relations between interacting signals and masks is consistent with the findings of neurophysiological and neuroanatomical studies of the auditory nervous system.
Backward Masking: Monotic and Dichotic Conditions
Authors: Elliott Lois L.
Published: September 2005

“Backward masking” is the term used to denote the situation in which one auditory stimulus is masked by another auditory stimulus which follows it in time while in “forward masking” the temporal positions of masking and masked signals are reversed. In this study, backward and forward masking were investigated for both monotic and dichotic conditions using white noise as the masking signal and a 1000-cps probe signal. Results indicate that monotic backward masking occurs over intervals up to 50 msec while, for the dichotic condition, backward masking occurs for intervals as long as 15 msec. Less monotic forward masking is obtained for brief masking intervals and very little dichotic forward masking is observed. These findings are considered in relationship to other experimental results.
Backward and Forward Masking of Probe Tones of Different Frequencies
Authors: Elliott Lois L.
Published: September 2005

Backward and forward masking of 500-, 1000-, and 4000-cps probe tones were explored under monotic and dichotic listening conditions. Effect of probe frequency was found to vary with duration of the masking interval.
Variation of Sound Pressure above a Surface of Irregular Impedance
Authors: Heaps H. S.
Published: September 2005

When acoustic radiation is incident upon a nonuniform surface, the variation of surface impedance gives rise to scattered radiation of a form dependent upon the small-scale variation of the surface impedance. This scattered radiation is discussed in terms of the surface statistics for the case of a plane or spherical incident wave. In addition to the scattered radiation there is present a specularly reflected wave whose amplitude is dependent upon the surface impedance averaged over a few wavelengths distance of the surface so as to smooth out the small-scale irregularities. The received power of the specular wave varies with position of the receiver. If the surface impedance has a constant complex component together with a varying complex component of Gaussian distribution of amplitude and uniform distribution of phase, the probability distribution of received amplitude is expressible in terms of Bessel functions of imaginary argument if the constant component is real and in terms of incomplete gamma functions if the constant component is complex. The resulting calculations are tedious but are summarized in graphical form over a wide range of values of the constant and varying components of the surface impedance.
Fractional and Multiple Judgments of Loudness
Authors: Ham Lloyd B. , Biggs Frank , Cathey Everett H.
Published: September 2005

Data on loudness estimates at 60, 200, 500, 1000, 5000, and 10 000 cps were continued at the University of Arkansas from 1933 to 1959. A recalculation of all data to 1950 indicated that fractional judgments required a smaller decibel change of intensity than the corresponding multiple loudness estimates. This new result, hereafter referred to as the directional dependency, accompanied by a provisional explanation, was recorded in the Journal of the Arkansas Academy of Sciences in 1950, and reported together with certain additional experiments at the Second ICA Congress in June of 1956.

Since reluctance to accept unanticipated results is considerable, a new approach to a series of experiments designed to explore this directional dependency was preceded by review of a possible dynamical explanation. The follow-up experiments included the proposed dynamical explanation as a part of the experimental objective and included new methods in our laboratory for the recording of judgments.

The results of the earlier series have been confirmed, but a satisfying explanation has not been established.
Effect of Interaural Correlation on the Precision of Centering a Noise
Authors: Jeffress Lloyd A. , Blodgett Hugh C. , Deatherage Bruce H.
Published: September 2005

Subjects were asked to center a noise presented via earphones, by adjusting a delay line controlling interaural time differences. Various noise correlations were employed ranging from 1.00 to 0.10. Even in the latter case, which represents a signal to noise difference of −9.5 dB the subjects were able to perform well above a chance level.
Compressional Bone Conduction in Cochlear Models
Authors: Tonndorf Juergen
Published: September 2005

Animal experiments have suggested the possibility that the compressional mode of bone conduction might produce a displacement of the cochlear partition, even when the cochlear windows and all other potential pressure outlets are closed. This assumption was found correct for the case of a cochlear model. It executed so-called “distortional” vibrations, i.e., while its walls in one place moved inward, those in the other moved outward and vice versa. This mode of motion tends to keep constant the total volume of the enclosed incompressible fluids.

The two perilymphatic spaces are known to differ in volume. Distortional motion causes the volume difference to alternate, thus producing compensatory displacements of the partition. This is in contrast to the effect upon the partition of the translatory and antiphasic movements of the cochlear windows in response to air-conducted sound. When both windows are open, or only one is occluded, the displacement of the partition, due to bone-conducted sound, represents the combined result of distortional and translatory motion.

The generation of traveling waves, when input and output are distributed over the entire cochlear shell, as in bone conduction, is discussed in terms of general cochlear mechanics.
On Various Optimum-Array Transducer Patterns and Approximations
Authors: Zindler Richard E.
Published: September 2005

In this paper the nature of optimum polynomials and functions for equally spaced transducer arrays under various optimum conditions is considered. Optimum patterns considered are for (a) sum patterns with minimum beam width for a given degree of minor lobe suppression, (b) sum patterns with maximum beam width, (c) difference patterns with minimum beam width for a given degree of minor lobe suppression, and (d) difference patterns with maximum beam width and others. The problems of obtaining the optimum polynomials are discussed and various approximately optimum shading schemes are presented.
Determination of the Energy Reflection, Absorption, and Transmission Coefficients of Acoustical Materials
Authors: Caddy R. S. , Pollard H. F.
Published: September 2005

The measured absorption coefficients of acoustical materials are often misleading when the material is mounted in a manner which differs from the test procedure. It is suggested that the use of the energy reflection, absorption, and transmission coefficients of the material would obviate this difficulty.
Radiation Efficiency of a Linear Array of Point Sources with Periodic Phase Variation
Authors: Thiessen G. J. , Embleton T. F. W.
Published: September 2005

The phase of the sources in the array is considered to vary in a “zig-zag” manner. It is found that the amplitude of the zig-zag must be sufficiently great that the phase varies along the length of the source at the same rate as in the radiated wave, before an appreciable decrease in radiation efficiency occurs. It is thus qualitatively similar to the array with a linear phase variation, which it approaches more closely as the length of the zig-zag approaches the length of the array. However, the periodic phase variations result in properties similar to the ghosts arising from imperfect diffraction gratings. If the sources are excited by means of pulses whose timing varies periodically along the length of the array, then the phase will be a function of frequency. It is then impossible to make the source inefficient for all frequencies. Only bands of frequencies will be suppressed.
Pressure-Particle Velocity Relations for Pulses in the Near Field
Authors: Sobey A. E. , Horton C. W.
Published: September 2005

If the signal from an acoustic source consists of arbitrary pulses which are separated in time by an interval large compared to the length of the individual pulses, a series of simple mathematical operations performed on the pressure and particle velocity as measured at a point will yield an expression from which one can determine the distance between the source and the field point. The term containing the distance is measurable only in the near field and becomes less than 10% of other terms at distances greater than the wavelength corresponding to the dominant frequency of the pulse. The theory is presented for spherical and dipole sources. Experimental measurements made in air are presented for various pulse shapes from a dipole source and are compared with the theory. The effect of a noise background on the method is also considered.
A Basis for the Acoustical Study of Singing
Authors: Manen Lucie , Fry Dennis B.
Published: September 2005

A systematic classification of the tones which singers produce is necessary as a basis for spectrographic and for x-ray studies of singing. A three-dimensional system is proposed in which tones are classified according to (1) the type of voice quality, (2) the mood which the singer expresses, and (3) the vowel which is articulated. Three types of voice are generally distinguished—light, lyric, and dramatic—which depend on the position of the larynx and the configuration of other parts of the mechanism (particularly the epiglottis, the pharynx, and the root of the tongue). Configurations have been found for light voice, lyric voice, and dramatic voice, together with factors governing mood which the singer expresses. Larynx position and larynx action determine phonation; and articulation, the formation of the particular vowel, is grafted upon phonation. This system gives 27 possible combinations preliminary experiments suggest that physiological differences (as shown by x-rays) and acoustic differences (apparent in spectrograms) may be found regularly correlated with the differences of voice, mood, and articulation covered by the system of classification.
Researches on the Singing Voice
Authors: Sacerdote Gino G.
Published: September 2005

Some recent methods of electroacoustical analysis are employed to study separately the different parameters characteristic of the singing voice. The analysis is effected on the same musical phrase, which has been chosen of well-specified characteristics, as performed by different singers: some were famous artists, some instructed voices, some beginners. In particular, we take into consideration the timbre variations and the relations between amplitude and frequency vibrato. From this comparison we can draw some considerations that, without entering the field of musical aesthetics, can be interesting in the study of the particularities of the singing voice.
Acoustical and Organ Design for Church Auditoriums
Authors: Rienstra Albert R.
Published: September 2005

The acoustical design of a church auditorium is of equal importance to that of the architectural design. It is essential, then, that the acoustical design follow the laws of sound projection from the source to the listeners with maximum fidelity both for the listeners and for the performers. Church acoustics has varied from the dead, low reverberant type at one extreme to the excessively reverberant type at the other extreme. In between these extremes there is a range of good listening conditions for music and speech for all types of liturgy. Longer reverberant times than usual are recommended for small and medium size auditoriums. A new design of church auditoriums is submitted which is interesting in its novelty and still is practical from a modern architectural point of view. Organ design has passed through extremes such as the pure romantic and the baroque. Either in its extreme is undesirable for general church use. However, a middle of the road design which is not necessarily a compromise but which uses the best in both is suggested. The enhancement effect of reverberation on organ tone of all types is discussed. Also the space requirements for organs and some principles of organ design are mentioned. This paper is given to stress the musical point of view of church design to the acoustician and architect so that extremes in acoustics will be avoided in the future.
On the Influence of Reverberation Time on Performances of Bach's Organ Toccata in D Minor
Authors: Kessler John A.
Published: September 2005

Bach's familiar Toccata in D minor has been performed and recorded by E. Power Biggs in many different churches and concert halls, on many different organs. Performance times and the duration of pauses in the performance are studied in relation to reverberation times measured from the recordings.
Acoustics of School Music Rehearsal Rooms
Authors: Young Robert W. , Gales Robert S.
Published: September 2005

A survey of opinion among music teachers in the vicinity of San Diego reveals the feeling of a majority that: (a) a choral rehearsal room should be more reverberant than a band-orchestra room; (b) an orchestra rehearsal room should be more reverberant than a band room; (c) a rehearsal room for concert band should be more reverberant than one for a marching band; (d) the school auditorium should be more reverberant than the rehearsal room. In many schools only two large rooms are set aside specifically for music, so some compromise is necessary. The problem is further complicated by the fact that an orchestra absorbs about three times as much sound as does a band of the same size. The reverberation time was measured, as a function of frequency, in 30 music rooms variously judged from bad to very good. The typical volume of a band-orchestra rehearsal room was 25 000 ft3, a choral room 20 000 ft3. The measured reverberation times at 500 cps in the empty rooms varied from 0.4 to 2.3 sec. From a preliminary correlation of judgments and measurements, the preferred reverberation time for a band-orchestra room is in the neighborhood of 1.0 sec or less. The preferred reverberation time for occupied choral rehearsal rooms is in the vicinity of 1.1 sec. These times for rehearsal rooms are slightly shorter than those sometimes recommended for performance of music in rooms of the same volume.
Transient Response of Loudspeaker Paper Diaphragms
Authors: Alons L.
Published: September 2005

Response curves of loudspeakers have irregularities, mostly not visible in the case of a loudspeaker of good quality and measured with normal equipment. By enlarging the ordinate scale these small peaks and dips of ±2 db become visible, but with the design of a cone it is considered that these irregularities are more or less inevitable and not so serious. This opinion is strengthened because by listening tests with a variable audio-frequency nothing abnormal can be detected. It is also impossible to measure any distortion in the region of these peaks and dips. By introducing short and sharp bursts of sine waves, however, all sorts of spurious oscillations between the bursts are visible on a cathode-ray tube. The amplitude of these phenomena depends on the internal damping of the diaphragm, the choice of the fiber, and the degree of beating of the pulp. The purpose of this paper is to raise the following question: Is this phenomenon the cause of the apparent harshness, etc., when listening to high-level high-note reproduction?