bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Vibration of Mass-Loaded Membranes
Authors: Kornhauser E. T. , Mintzer D.
Published: September 2005

The conventional treatment of a vibrating membrane with a small mass load, originated by Rayleigh, leads to perturbed eigenfrequencies slightly lower than the unperturbed values and independent of the area of the load so long as it is small compared to the area of the membrane. It is shown that this result is incorrect because of an invalid initial assumption about the amplitude of vibration of the load. Actually the perturbed frequencies are slightly higher than the unperturbed values, depend upon the area of the load, and approach the unperturbed values as the load approaches point mass. In addition a very low frequency mode exists whose frequency approaches zero as the load becomes smaller in area; this mode represents a perturbation of the trivial zero-frequency solution in the unperturbed case. The special case of a circular membrane loaded at the center is discussed in some detail.
Wave Propagation in a Randomly Inhomogeneous Medium. I
Authors: Mintzer David
Published: September 2005

The propagation of sound pulses from a point source in a medium where the index of refraction varies randomly is studied by means of the Born approximation to the wave equation. The coefficient of variation (standard deviation of the amplitude of a series of pulses, expressed as a percentage of the mean amplitude of the series) is evaluated for pulse lengths short compared with the time in which the refractive index varies significantly, and for ranges large compared with the wavelength of the sound. The results are in agreement with the experiments of Sheehy.
Acoustic Streaming at High Reynolds Numbers
Authors: Andres J. Milton , Ingard Uno
Published: September 2005

The apparent discrepancies between the observations of Andrade and Schlichting and those of Carrière with regard to the direction of acoustic streaming near obstacles has been reexamined. It is pointed out that the geometry of the streaming is determined by the two dimensionless parameters R = U0a/v and s/a, where R is the Reynolds number, U0 the velocity amplitude of the incident wave, a the characteristic length of the obstacle (radius of cylinder), v the kinematic viscosity and s the displacement amplitude of the incident sound wave. It is found that the Andrade-Schlichting observations correspond to large values of R (∼1000), whereas the Carrière observations correspond to small values of R (∼10). The present paper deals specifically with the theory for large R and extends the work of Schlichting to discuss the distortion of the flow pattern as a function of the sound intensity. The case corresponding to small Reynolds numbers is treated in an accompanying paper. The results obtained are found to be in agreement with experiments.
On the Theory and Design of Acoustic Resonators
Authors: Ingard Uno
Published: September 2005

Absorption and scattering from resonators in a free field as well as in walls are discussed. The effect of different aperture geometries on the resonance frequency of resonators is considered and illustrated by examples. Considering losses due to viscosity, heat conduction, and radiation, the optimum design for maximum resonance absorption is analyzed, and the results are expressed in terms of design charts. Nonlinear effects on the absorption and resonance frequency are also included, and a discussion of the onset of turbulence is presented.
A Tone Burst Generator
Authors: Onder Kerim
Published: September 2005

A tone burst generator is described for the production of electronically keyed oscillations free of transients. The unit consists of an oscillator, a keying circuit, and a negative pulse generator with variable duration and repetition rate. The advantages of the tone burst method in testing the frequency and transient response of amplifiers and transducers are pointed out. Some applications including reverberation time measurements are also mentioned. The almost instant rise and decay of the tone bursts was achieved by providing practically zero impedance path to ground for the keying pulses.
The Question of Damage in Ultrasonic Therapy
Authors: Hueter T. F.
Published: September 2005

Criteria are suggested for ensuring the proper use of ultrasound in physical therapy and in particular for avoiding damage to patients.
Combined Translational and Relaxational Dispersion of Sound in Gases
Authors: Greenspan Martin
Published: September 2005

It is shown that for a special value of the Prandtl number the Stokes-Kirchhoff equation governing the propagation of sound in a fluid is factorizable even for complex values of the heat conductivity and specific heats. A solution allowing for the dispersion due to both translational and thermal relaxation is thus obtained in simple form for this special case which, however, is representative of many gases with considerable accuracy.
Transmission of Sound through a Stretched Membrane
Authors: Ingard Uno
Published: September 2005

The problem of sound transmission through a membrane stretched across a duct is analyzed rigorously. The integral equation for the velocity distribution of the membrane is set up and studied in the special case of a circular cylindrical tube. Equivalent circuits for the membrane are shown for the frequencies around the resonances and the antiresonances of the membrane. High transmission loss is commonly associated with a large mass, but it is clear that it can also be obtained with very little mass if stiffness rather than mass provides the high impedance.
Information of Elementary Multidimensional Auditory Displays
Authors: Pollack Irwin , Ficks Lawrence
Published: September 2005

The information transmission associated with elementary auditory displays consisting of a large number of independent stimulus aspects, e.g., the frequency or the sound level of a tone, was examined. In general, multiple stimulus encoding is a satisfactory procedure for increasing the information transmission associated with elementary auditory displays. Further, extreme subdivision of each stimulus aspect fails to produce substantial improvement in the information transmission.
Wave Propagation in a Randomly Inhomogeneous Medium. III
Authors: Mintzer David
Published: September 2005

The coefficient of variation for a series of sound pulses and the correlation function for successively received sound pulses are evaluated for arbitrary pulse length, using the assumption that the correlation function of the refractive index inhomogeneities is expressible as the product of time- and space-dependent functions. For the case of pulse length much less than the time constant of refractive index correlation function, the coefficient of variation is found to be independent of the pulse length, and the pulse-correlation function is found to be identical with the time-dependent part of the refractive index correlation function. Comparison is made with data obtained from Sheehy. An approximate calculation shows that the motion of source and receiver will distort the pulse-correlation function so that little information can be obtained from the data concerning the time dependance of the refractive index.
Acoustic Properties of the Refractive Media of the Eye
Authors: Begui Zia Esmail
Published: September 2005

The density and viscosity of the refractive media of the eye have been measured. The velocity of propagation for 5 mc sound waves is found to be 1497 m/sec for the aqueous humor, 1516 for the vitreous humor, and 1616 for the lens. The absorption coefficient was determined at 30 mc for the liquid part of the eye and at 3 mc for the lens.
Loudness Relations in Two-Component Tones
Authors: Small Arnold M. , Thurlow Willard R.
Published: September 2005

A two-component tone was presented under a number of frequency and intensity conditions. The loudness of each component and the total loudness of the combination were traced as the intensity of the higher frequency and were brought from masked threshold to well above masked threshold. Loudnesses were determined by equating the tone or tones under consideration to a comparison tone.

When the higher frequency of the pair was at or below 1000 cps, it showed a loudness loss, relative to its loudness when presented alone, at medium intensities above its masked threshold; but as its intensity was increased, it tended to regain its normal loudness. When the higher frequency of a pair was above 1000 cps, it exhibited a greater than normal loudness at medium intensities above its masked threshold which again approached normal with increased intensity. The lower frequency of a pair seemed to be little affected by increases the intensity of the higher frequency within the limits of intensity used. Total loudness tended to be the algebraic sum of the components' loudnesses. The results indicate that the effect of a tone upon the loudness of another is not so simple a phenomenon as a tone's effect upon the threshold of another.
Transducer Output by Reaction Measurements
Authors: Kiernan Earl F.
Published: September 2005

Sound power output of a plate type transducer is obtained by measuring the reaction force on the transducer.
Vibrations of Indian Musical Drums Regarded as Composite Membranes
Authors: Ramakrishna B. S. , Sondhi Man Mohan
Published: September 2005

Raman first observed that the overtones of the Indian musical drums, Mridanga and Thabala, form a sequence of five natural harmonics, and that they result from nine modes of vibration, some of which are (approximately) degenerate. After a brief review of the previous work on the subject, a theory of these drums is developed in the present paper on the basis that the drumheads of these instruments can be regarded as circularly symmetric membranes with a radial step discontinuity the density. The eigenvalues and eigenfunctions of such a composite membrane are obtained, and it is then shown from a numerical calculation that for suitable ratios between the densities and radii of the two parts, the frequencies and the modes of vibration are in accordance with Raman's observations. Measured values of the frequencies of the first nine modes confirm the approximate degeneracies and the harmonicity indicated by the theory and establish the adequacy of the composite membrane as a mathematical idealization of these drumheads.
Ultrasonic Relaxation and Its Relation to Structure in Viscous Liquids
Authors: Litovitz T. A. , Lyon T. , Peselnick L.
Published: September 2005

Measurements of ultrasonic propagation of longitudinal waves in pentachlorobiphenyl were made over a large range of viscosity at frequencies in the range 7.5 to 52.5 Mc. The data at low viscosities demonstrated the presence of both shear and compressional viscous processes. Measurements in the relaxation region indicated that a single relaxation time theory could not explain the results. Several possible explanations are discussed. The data at very high viscosities showed a frequency independent absorption loss per wavelength, which indicated the possible presence of a nonrelaxational type of hysteresis.

The thermal coefficient of the high-frequency velocity was measured and found to be about twice the coefficient of the low-frequency velocity. The thermal coefficients of the instantaneous elastic moduli are compared to the low-frequency elastic moduli. It was concluded that the differences in the temperature dependence of these moduli could be related to the changing degree of order in the liquid.
Noise Level and Mechanical Stresses in Plastic Sound Records
Authors: Keller Ernest A.
Published: September 2005

Residual mechanical stresses in press-polished plastic film material used for the embossing type sound recording are in many cases responsible for relatively high noise levels. Results of noise measurements of different plastic materials on a 400 grooves per inch recorder are presented. The relation between optically observed stresses and recorded noise level is given. Practical consequences are discussed.
Burner Oscillations of the Gauze-Tone Type
Authors: Putnam Abbott A. , Dennis William R.
Published: September 2005

Acoustic oscillations produced when a flame burns from a grid in an 8-in.-diameter chamber were studied. The similarity between these oscillations and the Rijke gauze tones is pointed out. A theory is proposed for the gauze tones which is based on a phase lag between changes in flow rate and changes in heat-transfer rate. The predictions of the theory are shown to agree with test results. Indirect confirmation of the theory is given, but more work remains to be done before the theory can be completely proved or disproved.
Time Factors in Relative and Absolute Pitch Determination
Authors: Bachem A.
Published: September 2005

Error measures of pitch discrimination were obtained as a function of the time lapse between standard and comparison tones. The time interval ranged from one second to one week, establishing a “curve of forgetting.” Half of the subjects possessed absolute pitch. Results indicate that for short time intervals there is no observable difference in pitch discrimination between the two groups of subjects. With longer intervals there is a decided discrepancy, so long as the tone is within the musical range. This discrepancy in time-error curves is attributed to the shift from relative pitch comparison to chroma identification by those subjects possessing absolute pitch. The lack of discrepancy at the upper border of the musical frequency scale is attributed to chroma fixation. The curves of forgetting are more sigmoidal than straight logarithmic, particularly in the case of absolute pitch.
Hearing Losses of Aircraft Repair Shop Personnel
Authors: Webster J. C.
Published: September 2005

The Navy Electronics Laboratory's warble-tone audiometer test was administered from magnetic tape to 1133 overhaul and repair shop personnel. They were tested in groups of 18. The results were analyzed (1) by percentiles within each ten year age grouping, and (2) by classifying each audiogram into one of four deafness categories: normal, conductive, nerve, and mixed. In both analyses the results were compared to similar analyses on a large reference non-noise-exposed population.

The results show that roughly half the population is not adversely affected by noise. The worst hearing quarter of the noise-exposed population show considerable hearing losses especially at the higher frequencies when compared to the worst hearing quarter of the nonexposed population. The number of audiograms classified as “normal” drops from 78 percent to 66 percent, and the number classified as nerve deafness increases from 10 percent to 22 percent when the noise-exposed population is compared to the nonexposed population.

A set of masking contours is included on a sound-level chart so that knowing the noise level in a prospective test room, the minimum level of hearing loss that can be measured in that room can be readily determined.
A Note on Autocorrelation Analysis of Speech Sounds
Authors: Huggins W. H.
Published: September 2005

By separating a speech wave into its temporal and structural factors, it is possible to reveal concisely and explicitly how the vocal cavity characteristics and the periodicity of the laryngeal excitation enter into the autocorrelation function of the speech wave. This representation provides a simple explanation for the differences between the conventional spectrogram and the correlatogram, such as the marked sensitivity of the latter to variations in pitch and other nonphonemic qualities of the voice, which have been described in a recent paper by Biddulph. A scheme for using cross correlation to avoid the quadratic suppression of weaker components in the autocorrelation function is suggested.
The Multiple Panel Sound Absorber
Authors: Becker E. C. H.
Published: September 2005

The sound absorber is treated as a complex acoustic circuit in which the number of elements is multiplied to increase the absorption band width, particularly at low frequencies. A convenient form of construction is developed from a uniform array of simple cavity resonators set in a plane wall. Zero and pole frequencies are controlled and reduced relative to construction thickness by discrete addition of branch tanks. A common point technique is used for assessing optimum construction form and damping. Because of the large number of design parameters, use is best made of simple, approximate expressions for circuit elements, tempered by measured relations between standing wave patterns and impedance characteristics. For a given level of required high absorption, construction thickness determines low frequency limit and number of elements determines band width. An example of most favorable construction form is given, the performance of which compares favorably with other absorbers.
Air-to-Ground Sound Propagation
Authors: Parkin P. H. , Scholes W. E.
Published: September 2005

The attenuation of sound in air, in the vertical direction, has been measured on six occasions using an aircraft flying at various heights over a microphone at ground level. It was found that there was always negligible attenuation at frequencies below 1000 cps even though the air was turbulent; at higher frequencies the attenuation was found to be of the same order as the Knudsen-Kneser results for attenuation due to molecular absorption.
Auditory Sensitization
Authors: Hughes John R.
Published: September 2005

This experiment studied the lowering of the absolute auditory threshold that follows low-tone stimulation. Monaural thresholds were determined continuously with a recording audiometer before and after the ear was exposed to a pure tone. The frequency, intensity, and duration of both the exposure tones and the test tones were varied. Auditory sensitization was found to be a general effect among seventeen subjects. The magnitude of the effect was investigated intensively with three subjects. Their results demonstrated that sensitization produced by a pure tone is nonspecific: a given tone can sensitize the auditory system to a relatively wide range of test frequencies. Conversely, a relatively wide range of exposure frequencies can sensitize the auditory system to a given test tone. This nonspecificity is consistent with what we know, through microelectrode studies, about the spread of energy on the basilar membrane and the spread of excitation in the auditory nervous system. Contralateral sensitization effects were found.
Conductivity and Viscosity Effects on Wave Propagation in Piezoelectric Crystals
Authors: Kyame Joseph John
Published: September 2005

The effect of electrical conductivity and viscosity of the piezoelectric medium propagating plane waves has been studied. The solution of Maxwell's field equations and Newton's law of force in the general medium gives the modified elastic, piezoelectric, etc., constants necessary for determining the phase velocities of the plane waves. These modified constants are found to be complex and frequency dependent. Thus the propagation constants for the waves are complex and frequency dependent.

A particular example, propagation in the 1-direction of ammonium dihydrogen phosphate, is considered.
Perstimulatory Auditory Fatigue for Continuous and Interrupted Noise
Authors: Carterette Edward C.
Published: September 2005

Perstimulatory fatigue, or adaptation, is measured by a simultaneous loudness balance or median plane localization of a dichotically presented acoustic stimulus. After one ear has been stimulated for a period of time, it is usually found that the variable or comparison stimulus must be reduced below the prefatiguing intensity in order to maintain the loudness match or localization balance.

Five observers made median plane localizations of a continuous 100–5000 cps band-pass noise before, during and after a seven-minute fatiguing period. The fatiguing stimuli were continuous noises at 30, 60, 87, and 100 db SPL, and noises interrupted at 1, 2, 5, 9, and 12.5 ips with both burst level and noise-time fractions held constant at 90 db SPL and 0.5, respectively.

It was found that (a) the time required for fatigue to reach an apparent asymptote is at least seven minutes, about twice that required for pure tones; (b) the maximum fatigue increases with the intensity of the fatiguing stimulus and the function is positively accelerated; (c) for a fixed intensity of fatiguing noise, the maximum fatigue for the highest rate of interruption used (12.5 ips) is less than that obtained with a continuous noise having the same over-all level (87 db).

During the course of fatigue, the between-observer variations (standard deviations) of the balances tend to be greater than the within-observer variations; the reverse is true for the post-fatigue period.
Influence of Stimulus Duration on the Pure-Tone Threshold During Recovery from Auditory Fatigue
Authors: Jerger James F.
Published: September 2005

Comparison of the threshold shifts for 500, 50, and 5 millisecond short tones following a two-minute exposure to thermal noise at an over-all SPL of 110 db re 0.0002 microbar revealed disturbance of the pre-exposure time-intensity relationship for threshold during the post-exposure period. The pattern of this disturbance was similar to that which has been described by other investigators in the ear with Organ-of-Corti-type hearing loss. Thirty seconds after the termination of the noise the pre-exposure intensity differential among these three short tone durations was markedly reduced. As post-exposure time increased, the decline in the degree of temporary hearing loss was accompanied by a gradual return to the pre-exposure time-intensity relationship.
Pitch Perception for Certain Periodic Auditory Stimuli
Authors: Thurlow W. R. , Small A. M.
Published: September 2005

Results of experiments performed to determine the pitch characteristics of pulsed tones are reported. For most of the experiments, the pulsed tones were produced by passing brief rectangular pulses through band-pass filters. For a carrier frequency of 1000 cps pitch corresponded most closely to the rate at which the pulses were presented; no pitch corresponding to the carrier frequency was heard. For a carrier frequency of 5000 cps both low and high pitches were heard. The pulsed tones were used at low sensation levels, and spectral analysis showed that no low frequency corresponding to the pulse rate was present. Experiments with two pulsed-tone stimuli presented to the same ear showed that additional pitches were produced, depending on the time separation between pulses. An interpretation was suggested in terms of a neural “sorting out” process.
On the Contribution of a Contained Viscous Liquid to the Acoustic Impedance of a Radially Vibrating Tube
Authors: Robey Donald H.
Published: September 2005

The impedance presented to the inside surface of a hollow, liquid filled, radial cylinder of finite length has been determined theoretically. It was assumed that the liquid was retained by pressure-release caps or one pressure-release cap and one rigid cap at each end. For a loss-free liquid it is shown that the reactance presented to the cylinder wall becomes infinite whenever the liquid has a longitudinal or coupled radial resonance.

A sizeable resistance may appear when a viscous liquid is used. This is because the geometry of the arrangement is ideal for creating large shear losses. Exceptions to this occur for high frequencies where the wavelength is small in comparison to the cylinder length.
Response of an Elastic Plate to Localized Driving Forces
Authors: Lyon Richard H.
Published: September 2005

The vibration of an infinite elastic plate when driven by a localized driving force is studied theoretically. The dilation and shear potentials are expressed as Fourier integrals, the boundary conditions are applied, and the integrals evaluated by the calculus of residues. It is found that the motion of the plate may be represented by a discrete sum of nonorthogonal eigenmodes. These modes represent two types of waves, propagated and attenuated. The former are obtained from previous work on coincidence transmission. The latter are calculated by a graphical method, and presented in such a manner that they tie in continuously with the propagated modes. Certain unresolved features of the problem are discussed. One previous application of the theoretical results is disclosed.
Underwater Ultrasonic Scattering by a Radial Cylindrical Temperature Gradient
Authors: Grant P. E.
Published: September 2005

The scattering of a one-megacycle underwater ultrasonic beam by a radial cylindrical temperature gradient perpendicular to the beam is studied as a function of position and gradient strength. The gradient is produced by a vertical hot wire. The presence of free convection currents makes necessary time average study of both the temperature and scattering distributions. From these studies average temperature and scattering distributions are constructed, and it is found that a possible diffractive transition region exists between temperature gradients of 14.5 and 26.5°C/cm. In addition, there is evidence that a transition from wave to ray acoustics occurs between gradients of 26.5 to 36.5°C/cm.
Elastic Constants of Aluminum from 20°C to 400°C
Authors: Zucker Charles
Published: September 2005

The use of the ultrasonic pulse technique as a means of determining the elastic constants of polycrystalline aluminum at high temperatures has been considered in some detail.

The C11 and C44 elastic constants, Debye temperature, and Young's modulus were computed from the longitudinal and transverse velocity measurements. The variations of these constants with temperature showed the predicted linear decrease expected from solid state theory.
Tonal Monaural Diplacusis
Authors: Ward W. D.
Published: September 2005

Two similar cases of tonal monaural diplacusis are described. When low-intensity sinusoids within a certain range are presented, several distinct tones are heard in addition to the tone presented. The effects are focussed at 3610 cps for one subject and at 3155 cps for the other. Pitch-matching and probe-tone techniques show that the additional tones correspond to combination tones expected in a normal ear stimulated by two tones, one of which is fixed at one of the above frequencies. Hence some basic instability of the auditory mechanism at these frequencies is indicated for these observers. It is suggested that the defect lies in the “peaking” process of the cochlea, so that an adequate explanation of the phenomena may be of some importance to auditory theory.
Variations in Sound Pressure Produced in Guinea-Pig Ears Due to Normal and Abnormal Eardrums
Authors: Benson R. W. , Eldredge D. H.
Published: September 2005

Sound pressures measured with a probe-tube microphone in front of the tympanic membrane of the guinea pig have been compared at 100-cps intervals in the frequency range 50 to 8000 cps to the sound pressures similarity measured in a speculum coupling an acoustic source to the ear canal. Rather different functions were obtained for each of five conditions: (1) normal, (2) hair-line slit in the tympanic membrane, (3) rupture of tympanic membrane, (4) fluid behind tympanic membrane, and (5) bulla open. The variability in each of the categories is presented. Variability was greatest in the normal ears and least in the bulla open ears.
Scattering of High-Frequency Sound Waves in Polycrystalline Materials
Authors: Bhatia A. B.
Published: September 2005

The scattering, and hence attenuation, of plane dilatational and shear waves due to random orientation of the grains is calculated on the assumptions that (1) the wavelength is large compared to the grain size and (2) the variations in elastic moduli from grain to grain are small compared to the average values of these moduli for the bulk material. Previous treatments of this problem are incomplete; for incident dilatational waves they are valid for a fluid (rigidity modulus=0), and for incident shear waves they describe inadequately the angular dependence of the intensity of the scattered shear waves. It is shown in this paper that for both of these types of incident waves both the scattered dilatational and shear waves are produced; the energy carried away from the incident beam by the latter is 32(Vl/Vs)5 times that by the former. Here Vl and Vs are the velocities of the dilatational and shear waves, respectively. The agreement between the theoretical and observed values of the attenuation coefficient is much better than that previously obtained by Mason and McSkimin.

The attenuation due to local fluctuations in the density of a medium caused by thermal agitation is also calculated. For solids and liquids this effect is completely negligible. However, for a gas near its critical point, this attenuation is appreciable and rises sharply as the critical point is approached.
Ultrasonic Absorption and Thermal Relaxation in CO2
Authors: Henderson M. C. , Klose J. Z.
Published: September 2005

Measurements of ultrasonic absorption have been made in dry CO2, and in CO2 with hydrogen admixtures, between 19°C and 146°C and at pressures from 0.1 to 650 atmos, and frequencies from 300 kc to 7 Mc. The absorption is described within experimental error by the relaxation formula throughout this range using either (a) a single relaxation time and a single relaxing specific heat representing the total of the vibrational modes, or (b) two relaxation times somewhat more than a factor of two apart, and two relaxing specific heats given by certain combinations of the component vibrations. The relaxation time, or times, varies inversely as the density throughout. The maximum absorption per wavelength comes at 32 kc/atmos at 25°C. Addition of hydrogen shifts the CO2 relaxation time by 110 kc/percent by volume of H2; this amount is in agreement with the shift determined by Knudsen and Fricke, provided their data is interpreted as being by volume and not by weight. The “classical absorption” at low pressures is 1.5 times the theoretical value.
Reproduction and Identification of Elements of Auditory Displays
Authors: Pollack Irwin , Johnson Lawrence B.
Published: September 2005

The identification of the frequency of a tone was examined under four training procedures. The training procedures attempted to determine whether identification of tonal frequency could be improved by attaching distinctive motor responses to elements of the display. For relatively short training periods, such procedures were little more effective than simply providing verbal information of the correctness of the identification.
Impedance and Shock Spectra
Authors: O'Hara George J.
Published: September 2005

Attempts to combine shock spectra, by envelope of fiducial limit types of analysis, to produce curves useful for design purposes have led to design shock spectra which are extremely overconservative. It was noticed that this technique assumes that the impedance of any structure at its foundation for its fixed base natural frequencies is very low, and therefore unable to affect the foundation motion. This was in contrast to test evidence that a dip would appear in the regions of these frequencies in the spectrum plot. This paper examines the theory of shock spectra, Fourier spectra, and mechanical impedance to determine qualitatively the effect upon shock spectra of the dynamic reaction of structures. The concept of shock spectrum dip is presented, explained, and experimental verification exhibited. Several theorems regarding shock and Fourier spectra are advanced. The necessary distinction between shock spectrum values at fixed base natural frequencies of a structure and at natural frequencies of a structure-foundation combination is demonstrated. The potentially extreme overconservatism in design resulting from incorrect usage of shock spectra is pointed out.
Random Sound Field in Reverberation Chambers
Authors: Balachandran C. G.
Published: September 2005

A series of experiments were performed to compare the efficiency of different diffusing devices in producing a completely random sound field in a reverberation chamber and the effectiveness of some of the methods for judging whether a sound field is completely random. An additional experiment was performed to compare two types of test signals, viz., warble tone and the same nominal band width of random noise. Results of these measurements indicate the general superiority of the rotating vane over other diffusing devices and superiority of random noise over warble tone in producing a smooth decay curve. One of the significant conclusions is that even when the diffusion is reasonably adequate the measured absorption coefficient of a standard sample appears to vary with the chamber absorption especially at the high frequencies.
Evaluation of a Stereophonic Loudspeaker by Multiple Microphone Arrays
Authors: Carlisle Richard W. , Schwartz Arnold
Published: September 2005

There is a problem in measuring the sound distribution from a stereospeaker array to correlate the results of anechoic chamber measurements with listening tests in live listening rooms.

One method which is helpful is to measure the pressure at a large number of points in the live-room. A multiple microphone arrangement is described which facilitates such measurements, and its application to a stereophonic speaker system is illustrated.
Effects of a Progressive Ultrasonic Wave on a Light Beam of Arbitrary Width
Authors: Hargrove L. E. , Zankel K. L. , Hiedemann E. A.
Published: September 2005

This study is a theoretical and experimental investigation of the effects of a progressive ultrasonic wave on a light beam of small but arbitrary width. Theoretical development of the results given recently by Zankel [Naturwissenschaften 46, 105–106 (1959)] is presented. The effects of finite amplitude distortion are considered. Measurements of the time-average intensity distribution in the broadened source slit image are made for varied light beam widths and sound pressures in water at 1.0 mc. and these experimental results are compared with the theoretical results. Previous work of others is discussed in terms of the derived expressions.
Sound Velocity in Water above 212°F
Authors: McDade J. C. , Pardue D. R. , Hedrich A. L. , Vrataric F.
Published: September 2005

The value of sound velocity in water at temperatures above 212°F is needed for the use of acoustic devices, such as flowmeters or level meters, on water at these temperatures. The method consisted of heating water to temperatures above 212°F under pressure; propagating constant frequency sound signal through it, and using a phase meter to detect changes in wavelength due to changes in sound velocity. The change in sound velocity was computed from the change in wavelength. The value of the sound velocity was obtained by adding the measured change to previously known values below 212°F. It was found that the velocity of sound in water decreases much more than was anticipated from extrapolation methods, at temperatures above 212°F. The measurements show that the sound velocity decreases monotonically from 5066 ft/sec at 210°F to 3230 ft/sec at 550°F.
On the Variation of Acoustic Radiation Resistance in Water under Ultrasonic Cavitation
Authors: Kikuchi Yoshimitsu , Shimizu Hiroshi
Published: September 2005

The variation of acoustic radiation resistance of ultrasonic radiation in a cavitating liquid is studied as a function of acoustic intensity, and the pulse width of the radiation. Intensities up to 1.75 w/cm2 are employed and pulse widths down to 3 msec.
Scaling Human Reactions to the Sound from Aircraft
Authors: Kryter Karl D.
Published: September 2005

Studies were undertaken to (determine how “noisy” commercial jet aircraft will sound to people on the ground in comparison to present-day commercial aircraft with reciprocating engines. Three experiments involved the flyover sound made by reciprocating-engine aircraft (a DC-7 and a Super-Constellation) and jet aircraft (a Caravelle, a Comet, and a 707). People were asked to judge the “annoyance” or potential bother-someness of the sounds relative to one another.

It was found that the over-all sound pressure level (“C” scale) and the speech interference level (SIL) of the sounds from the aircraft as measured on the ground, either outdoors or indoors, bear little relation to the judgments. The loudness level in phons, the values obtained with the aid of the “equal listener-response curve” of Miller and Beranek, and over-all sound pressure level “A” scale and “P” scale correlate better with the findings. However, the results of the judgment tests are predicted best when the SPL's of the various octave bands are weighted in a newly prescribed manner. This calculation scheme is based on previously published equal-annoyance contours and the procedures developed by Stevens for calculating loudness level.
Noise Stress in Laboratory Rodents. II. Effects of Chronic Noise Exposures on Sexual Performance and Reproductive Function of Guinea Pigs
Authors: Anthony Adam , Harclerode Jack E.
Published: September 2005

Chronic exposure of male guinea pigs to intense, low-frequency noise (139–144 db, 300–4800 cps) for six weeks did not affect their sexual performance. Histological and histochemical analyses of various organs indicated noise is followed by increased activity of the adrenal glands. However, the absence of pathology in the reproductive and digestive organs indicated that the tolerance limits of animals were not exceeded.
Experimental Study of Bone Conduction in Ears with Mechanical Impairment of the Ossicles
Authors: Legouix J. P. , Tarab S.
Published: September 2005

The cochlear-microphonic potential of guinea pigs was recorded during stimulation by bone-conducted sounds. The amplitude and the phase of the response were measured while the ossicles were altered in various ways.

At low and middle frequencies, fixation of the ossicular chain produces a decrease of amplitude and a phase advance of about 70°, while an increase of the mass yields an increase of amplitude and a phase lag greater than 180°. A progressive increase of the mass, produced by introducing paraffin oil in the middle-ear cavity, yields a progressive variation of amplitude and phase and, at a particular moment, a complete disappearance of the response. Symmetrical results were obtained by altering the intrabullar pressure. All these results are interpreted as showing the participation of several mechanisms contributing to the whole response. At low frequencies a translational mechanism involves two components: one related to the motion of the ossicular chain and the other related to the motion of the perilymphatic fluid. These two components contribute to the whole response according to their amplitude and phase. At higher frequencies a compressional mode of bone conduction, independent of the motion of the ossicles, is responsible for the stimulation. These findings agree with the alteration of bone conduction observed in clinical cases and provide an explanation for the lateralization of the sound source in an ear affected by conductive deafness, as shown in the Weber test. This lateralization may be accounted for by the observed phase shifts.
Minimal Rules for Synthesizing Speech
Authors: Liberman A. M. , Ingemann Frances , Lisker Leigh , Delattre Pierre , Cooper F. S.
Published: September 2005

It has been found to be extremely difficult to isolate phonemic elements from recorded utterances or to synthesize speech by assembling prerecorded phonemic segments. One reason for the difficulty lies in the fact that the perceptually discrete phonemes are typically combined, and in some cases encoded, into units of essentially syllabic dimensions. As a result, prerecorded elements must, in many cases, approximate syllables, and the synthesis of speech by this means will require a large inventory of recordings. By taking advantage of knowledge about the acoustic cues for speech perception, however, it is possible to write rules for synthesis in terms of phonemes (rather than syllables) and thus reduce considerably the number of separate rules or items needed. Indeed, one can reduce the number of rules still further by writing them at the level of subphonemic dimensions, viz., place and manner of articulation. Several complicating factors make it impossible to achieve an ideal minimum. First, rules or rule modifiers must be added to take care of certain prosodic and positional variations. Failure to do so not only affects naturalness, but also impairs intelligibility, even at the level of segmental phonemes. Second, it is necessary in a few special cases to have different rules for a single consonant phoneme (or a dimension of that phoneme) before different vowels. This reflects the occasionally complex relation between phoneme and articulation on the one hand and sound output on the other; presumably, this complication would not affect the rules of synthesis for an articulatory model.

A system of rules for synthesis framed largely in terms of subphonemic dimensions is described with reference to an example. Words and sentences of rather high intelligibility have been synthesized by such rules.
Pure-Tone Cross-Ear Localization Effects
Authors: Thurlow Willard R. , Elfner Lloyd F.
Published: September 2005

Experiments are reported on the effect of a tone in one ear on the localization of a tone in the other ear. Localization effects were systematically explored with low frequencies at 30-db sensation level, the frequency in one ear being a simple n/1 multiple of that in the other. With this procedure, localization effects can be obtained between low-frequency tones (below 1000 cps) of widely differing frequencies. If multiples are not used, localization effects occur only within narrower frequency limits for low frequencies. Thresholds for difference between the frequencies in the two ears within which the localization effect occurs increase systematically as one goes from low- to high-frequency regions. The localization effects on a given tone cause this tone to be perceived as “pulled in” from the side location that it had when sounded alone.
Backward Masking
Authors: Pickett J. M.
Published: September 2005

An experiment was carried out to explore the auditory masking effect of a noise burst on a preceding weak stimulus. A short 1000-cycle tone preceded a burst of white noise by a variable silent interval. The threshold intensity level of the tone was taken as a measure of the masking provided by the noise burst. The effects were examined of combinations of the following conditions: tone durations of 5, 10, 15, 20, 25, and 50 msec; silent intervals of 0, 2, 5, 10, 25, and 100 msec; and noise burst levels ranging from 50 to 130 db SPL. Appreciable elevations of tone threshold were observed for silent intervals less than 25 msec. Threshold elevations increased progressively as noise burst level was increased. The latter effect increased with shorter silent intervals. The tone-noise interval was a more critical factor than tone duration.
Pure-Tone Masking
Authors: Small Arnold M.
Published: September 2005

The influence of one pure tone on the threshold of another was investigated. In contrast to previous experiments, masking in the present experiment was studied by determining the level of the masker necessary to mask a signal as a function of the frequency of the masker. The level and frequency of the signal served as parameters. The general forms of the masking functions are similar to those reported previously, but vary in several details. The maximum masking effect occurred when the frequency of the masker approximated that of the signal. When the masker frequency was greater than that of the signal the slope of the masking function was very steep, 150–280 db/octave depending upon signal level and frequency. This slope tended to be steeper at higher signal levels and, although less marked, also at higher signal frequencies. When the masker frequency was about 0.85 that of the signal an irregularity appeared in the masking curves. The size of this hump increased as signal frequency and level increased. Its frequency location seemed to rule out aural harmonics as a cause and its presence was tentatively related to perception of envelope modulation.

The data are discussed from the points of view of band-pass filter analog and compared to studies of previous investigators. In general the present findings represent an extension of pure tone masking data with wider ranges of stimuli and a different method than those previously used.
Design of Directional Arrays
Authors: Brown John L. , Rowlands Richard O.
Published: September 2005

From the application of information theory, it is found that for low signal-to-noise ratios, there is no better method of increasing the information content of a signal than to add the outputs of the elements of an array to improve the signal-to-noise ratio. When the signal-to-noise ratio is already high, however, the array should be designed so that independent information is supplied by each element when associated with a reference element.

The possibility of increasing directionality by nonlinear operations is then discussed. In particular, it is shown that, for the noiseless case, a two element array can be made to yield patterns equivalent to those produced by an n-element linear array. Linear maximum directivity arrays (in the sense of Pritchard) may also be synthesized with three omnidirectional elements and a number of nonlinear operations which remains invariant as the order of the equivalent linear army is increased.

Finally linear methods designed to minimize the mean squared error are considered and it is found that array rotation is capable of giving optimum results under certain circumstances.
On the Aerodynamic Noise of a Rigid Flat Plate Moving at Zero Incidence
Authors: Powell Alan
Published: September 2005

The aerodynamic noise resulting from the subsonic flow over a flat rigid plate at zero incidence has three origins. “Surface” noise due to fluctuating surface pressure is postulated to vanish by the author's image argument, except near the edges of the plate, where it is more appropriately called edge noise. Of dipole nature, its acoustic power depends on the velocity raised to between the fourth and fifth power, and consequently is to be expected to be of prime importance at low enough speeds. The contribution from fluctuating shear stresses is likely to be much smaller and so has been neglected. Quadrupole radiation takes place from from the turbulence of the boundary layer, producing layer noise and also from the turbulent wake, producing wake noise. Together, the latter two are suggested to have a spectrum with a single peak, bounded by slopes like f2 and f−7/4. Their noise power depends on nearly the eighth power of velocity, so is of increasing importance with speed. Analytical details rest on similarity concepts; the spectra in particular are subject to certain conditions. Also, the convection effects on the acoustical power and spectra are excluded on empirical grounds stemming from considerations of jet noise.
Survey of Thermal, Radiation, and Viscous Damping of Pulsating Air Bubbles in Water
Authors: Devin Charles
Published: September 2005

A theoretical discussion is presented on the fundamental processes by which pulsating gas bubbles in liquids dissipate their energy. The survey is limited to the case where the amplitude of the volume pulsations are assumed to be sufficiently small that the pulsations may be described by linear equations. A portion of the energy of the bubble system is lost by the radiation of spherical sound waves, a part is lost by heat conduction due to the polytropic compressions and expansions of the enclosed gas, and a portion is lost by viscous dissipation attributed to viscous forces acting at the gas-liquid interface. A survey is made of the procedures for measuring the resonant damping constant as described in the methods of successive oscillations, width of the resonance response, standing-wave ratios, and resonance absorption. Experimental results verify that the damping at resonance is due to thermal and radiation, and possibly viscous damping.