bluuebunny/crossref_metadata_2025 huggingface dataset:
Masking of Speech by Line-Spectrum Interference
Authors: Licklider J. C. R. , Guttman Newman
Published: September 2005

Two series of intelligibility tests were conducted. In the tests, speech was presented against a background of interference. The line-spectrum interference consisted of from 4 to 256 sinusoids, superposed in a linear adder. Three different spacings of the components in frequency, and several different distributions of power among the components, were studied. Tests with continuous-spectrum random noise were made for comparison.

The over-all interference power required to reduce intelligibility to a given level decreases as the number of components in the interference increase. The drop is about 10 db in the decade from 4 to 40 components. Beyond 40, there is much less change. Even 256 components, however, mask measurably less effectively than random noise of equivalent power in the band 200–6100 cps. For a given number of components, the line-spectrum interference most detrimental to intelligibility has the same number of components in each frequency band of equal contribution to intelligibility, and its components are uniform in amplitude. The bearing of these findings on the theory of intelligibility and on procedures for predicting intelligibility from physical parameters is discussed.
On the Relation between the Intelligibility and Frequency of Occurrence of English Words
Authors: Howes Davis
Published: September 2005

The threshold of intelligibility for a word in a wide-spectrum noise is shown to be a decreasing function of the frequency with which the word occurs in general linguistic usage (word frequency). The drop in threshold is about 4.5 db per logarithmic unit of word frequency. This rate is independent of the length of the word, although the thresholds for words of given frequency of occurrence are lower for long words.

The effect of restricting the listener's alternatives in an intelligibility test to a specified number of words is calculated from this relationship. These calculations come within 1 db of published experimental data. Theoretical functions relating intelligibility threshold to word length are also calculated from the word-frequency effect, on the assumption that listeners can discriminate the length of a word at levels too low for it to be identified. These functions are in general agreement with the experimental results.

Implications for intelligibility testing procedures are discussed.
Some Experiments Related to the Noise from Boundary Layers
Authors: Hubbard Harvey H.
Published: September 2005

This paper presents the main results of several recent experiments relating to the generation of noise in boundary layers. An attempt is made to correlate data obtained from a wind tunnel, a rotating disk, a helicopter rotor, and an aircraft in flight. These data provide evidence as to the mechanism of noise generation in the boundary layer and show how the noise varies as a function of velocity, density, and surface roughness. Some discussion also given with regard to the relative importance of the boundary layer noise and the noise from the power plant in high-speed jet aircraft.
Effect of a Negative Impedance Source on Loudspeaker Performance
Authors: Werner Richard E.
Published: September 2005

A direct radiator moving coil loudspeaker driven by an amplifier whose output impedance approaches the negative of the blocked voice-coil impedance can be made to exhibit extended low-frequency response with reduced distortion. The effect of the system is in some ways analogous to a manyfold increase in loudspeaker efficiency. In a typical case, neutralization of 70% of the blocked voice-coil impedance completely damps the cone resonance, as well as substantially reducing the nonlinear distortion below resonance. When the amplifier is compensated for the falling radiation resistance at low frequencies, uniform output can be obtained to any arbitrary low frequency, limited only by the ultimate power-handling capability of the amplifier and speaker. In this system, no additional amplifier power is required at frequencies down to the speaker resonance; additional power is required below that point.
Acoustical Time Regulator
Authors: Springer Anton M.
Published: September 2005

The paper describes a device for altering the speed of reproduction of tape recordings, by mechanical means, without altering the frequency and therefore the pitch.

The playback time can be changed within a range of 50–200% of the recording time. Although there are no technical limits to the range of time-change, certain loss of quality begins to become apparent if the time-change is increased beyond ±30%.

The possibilities of application are also discussed.
Radiation Load on Arrays of Small Pistons
Authors: Toulis W. J.
Published: September 2005

The radiation load on a piston in an array is examined, preliminarily, through the correspondence of a piston in an infinitely long tube and in a conical horn to arrays on an infinite plane surface and on a rigid sphere, respectively. The evaluation of the velocity potential for the two arrays suggests that the average radiation load on an array consists of two terms. The principal term arises from a uniform distribution of the total source strength over both active and inactive areas of the array. The secondary term corresponds to the free space load for one of the pistons but reduced in magnitude by a factor proportional to the average separation between adjacent pistons.
On Presenting the Output of a Mechanical Speech Recognizer
Authors: Fry D. B. , Denes P.
Published: September 2005

The output of a mechanical speech recognizer consists of a series of units which are closely correlated with the phoneme sequence which forms the speech input to the system. This output has to be transformed and presented to the human “reader,” usually in one of two ways, either by using it to reconstruct audible speech sequences or by presenting it in a sequence of visible characters. In both cases, the success of the recognizer will depend greatly on the degree to which good use can be made of the reader's existing linguistic knowledge, and methods of assessing its success must take this fact into account. This paper will present the results of experiments designed to compare methods of presenting the output and also methods of measuring the performance of the recognizer in terms of the ease with which the “reader” can reconstruct the input.
Method of “Single Descent” in Group Audiometry
Authors: Dixon Ward W.
Published: September 2005

Various methods for determining threshold in a group testing situation were compared. No significant differences in reliability were found between the method of adjustment (either direct or indirect) and the method of “single descent,” in which the listener presses a button “just when the beeps disappear.” However, the method of single descent is independent of individual differences in adjustment time and requires less apparatus. Thresholds determined by single descent were affected only slightly by rate of descent, starting level and practice factors. A comparison between single descent and the standard clinical technique showed the thresholds to be valid. Field performance of the method, in a 10-man group audiometer, has fulfilled expectations from the pilot studies.
New Equation for the Asymptotic Field Amplitude in a Two-Dimensional Inhomogeneous Medium
Authors: Kay Irvin
Published: September 2005

The geometrical or high-frequency approximation to solutions of the two-dimensional wave equation in an inhomogeneous medium is considered. A new ordinary differential equation for a quantity which is inversely proportional to the geometrical high-frequency field intensity (the square of the field amplitude) is derived. This equation, along with the standard ray and phase equations form a system form which a complete wave solution in the high-frequency asymptotic limit can be calculated numerically, e.g., through the use of a differential analyzer. The examples of a homogeneous medium and a plane stratified inhomogeneous medium are discussed, and the results of the preceding analysis are verified in these two special cases.
Note on Acoustic Radiation Pressure
Authors: Awatani Jobu
Published: September 2005

A method of obtaining the acoustic radiation force (i.e., the process of integrating the force on every surface element of the object placed in sound waves) is criticized. This process yields the sum of the contribution of the true radiation pressure and that of the mean pressure. Though there is no effect in plane progressive waves, the mean pressure has a considerable effect on the result obtained in plane standing waves or progressive spherical waves.
Structural Fatigue under Combined Sinusoidal and Random Vibration
Authors: Spence H. R. , Luhrs H. N.
Published: September 2005

Structural fatigue caused by combined sinusoidal and random vibration is of concern in flight proofing of electronic equipment, since such excitation is required by many current ballistic missile equipment specifications. How to predict the fatigue under this vibratory excitation is discussed with particular reference to the relationship of combined vibration to a single sinusoidal substitute.

Equations and curves for obtaining the sinusoidal substitute are presented and their application illustrated on a single resonator system.
On Vibrations of Shallow Spherical Shells
Authors: Kalnins A.
Published: September 2005

The vibration analysis of shallow spherical shells is extended to (a) frequencies of the order of magnitude of the first thickness-shear mode in an infinite plate and (b) moderately thick shells. A tenth-order system of three uncoupled differential equations is derived, which govern the nonsymmetric dynamic deformation of a shallow spherical shell subjected to arbitrary time-dependent surface loads, and separable solutions are obtained in terms of Bessel functions. As an example, a frequency equation is deduced for the determination of natural frequencies higher than those accurately predicted by the classical theory for free vibration of a shallow spherical cap with a clamped edge.
Complex Image Theory of Low-Frequency Sound Propagation in Shallow Water
Authors: McLeroy E. G.
Published: September 2005

The problem of propagation of low-frequency sound in shallow water over several layers and a basement is approached through an image theory in which the first thin layers are lumped together with the water layer. This effective structure is assumed on the basis of expected good transmission through a thin layer (less than one wavelength thick having acoustic properties not very different from those of its bounding media. The required reflection coefficient at the lower boundary of the lumped layer, expressed as a function of range and the order of the image source of a ray, is taken in the form given by Abelés for reflection of plane waves from a layered system. The theory yields calculated transmission loss functions which show reasonable agreement with experimental results. Comparisons of theoretical loss and data obtained at Panama City, Florida, are made over the frequency range 6–244 cps.
Critique of the Reverberant Room Method of Measuring Air-Borne Sound Transmission Loss
Authors: Mariner Thomas
Published: September 2005

Some obscure but important philosophical difficulties with the standard method of measuring transmission loss by the reverberant room method have led to reexamination of the basic concepts. An equation is derived relating transmission loss to the “total loss area” H2 of the receiving room. H2 is found to be measurable within a negligibly small uncertainty, using familiar sound-decay techniques, providing that T2/T1, the ratio of “natural” reverberation times of the receiving and source rooms is properly adjusted. It is shown that the equations commonly used in the existing standard method require knowledge of A2, the total absorption of the receiving room, implicitly excluding transmission through the panel. A2 is not generally measurable without prior knowledge of the transmission loss of the test panel. These and other considerations result in the proposal of a new procedure.
Kirchoff-Helmholtz Absorption in Wide and in Capillary Tubes at Audible Frequencies
Authors: Mariens P.
Published: September 2005

The acoustic amplitude attenuation constant has been measured in air for pressures from 2.3 to 0.18 atmos in a cylindrical tube of 5.16 cm diameter and in cylindrical capillary tubes of 0.10 and 0.15 cm diameter. In the first series of measurements the amplitude of stationary waves in the wide tube is measured as a function of the distance from the end, and the attenuation constant calculated. In the second series of measurements the measuring tube is dosed by a sample of capillary tubes; the absorption coefficient and the phase difference at the input of the samples are measured and from that the attenuation in the capillary tubes is calculated. In both cases it is found that the theoretical values of Kirchhoff-Helmholtz are about 13% lower than the mean experimental ones.
Low-Frequency Pure Tone Masking
Authors: Finck Alfred
Published: September 2005

Binaural masked thresholds from 50 cps to 4800 cps were measured using low-frequency (10, 15, 25, 30, and 50 cps), high-intensity (100, 115, and 130 db SPL) pure tones. The results obtained for 5 listeners demonstrate a broad masking spread with masking peaks for 130-db SPL pure tones.
Thermal Relaxation in Carbon Dioxide as a Function of Temperature
Authors: Shields F. Douglas
Published: September 2005

Sound absorption and velocity measurements have been made in carbon dioxide between 0 and 200°C. The relaxation absorption was isolated by subtracting the tube and classical absorptions from the measured absorption. The Kirchhoff equations, which had been justified previously by measurements in A and N2 were used to make these corrections. From the relaxation absorption were determined the temperature variation of the thermal relaxation time, the transition probability, and the collision efficiency. The results indicate that for the frequencies and pressures here employed the relaxation absorption and velocity effects are a function of f/p. This means that only binary collisions are effective in transferring energy between the vibrational and translational modes. The relaxation theory with a single relaxation time for all the vibrational modes adequately predicts the observed absorption and velocity. It is estimated that a separation in the relaxation times of the two lowest modes by a factor of more than two could not have gone undetected at 100°C. The temperature variation of the collision efficiency was adequately predicted by the Landau-Teller equation.
Steady Rotational Flow Generated by a Sound Beam
Authors: Tjötta Sigve
Published: September 2005

This is a theoretical study of the streaming generated by an ultrasonic sound beam in a fluid. A stream-function is introduced, and the differential equation giving it is solved by means of a Green's function.
Further Studies of the Influence of Acoustic Microstreaming on the Photographic Development Process
Authors: Jackson Francis J.
Published: September 2005

A major obstacle in attempting quantitative investigations of the influence of microstreaming on solid-liquid interface reactions has been the inability to prevent gaseous cavitation (which destroys the orderly streaming action) from occurring in the liquid medium when the latter is subjected to a high-amplitude sound field. The present article describes a modification of an earlier experimental arrangement, used to study microstreaming effects on a specific interphase chemical reaction (i.e., development of a photographic emulsion), which incorporates a means for suppressing undesired cavitation. Preliminary results obtained using this apparatus are presented. These results permit a more precise correlation between observed effects and properties of the streaming field than has hitherto been possible. Preliminary data indicating the extent to which microstreaming affects the local development rate are also presented.
Tube Corrections in the Study of Sound Absorption
Authors: Shields F. Douglas , Lagemann Robert T.
Published: September 2005

The absorption and velocity of sound in argon, nitrogen, and carbon dioxide have been investigated over a range of frequency, pressure, and temperature conditions. Use was made of a movable sound source and a stationary microphone, both employing the principle of the ribbon microphone, located inside glass tubing 1.73 cm in diameter. It was found that Kirchhoff's equations correctly predicted the absorption and velocity as the temperature was varied from 0 to 200°C in the case of argon and from 0 to 150°C for N2. Not only did the tube absorption vary as a function of (f/p)12, but the factor incorporating the physical properties also appears to be valid. Certain earlier experiments have not agreed with the Kirchhoff predictions of the magnitude of the factor which depends on the physical properties, and the success in checking the theory is attributed to the use of improved data for the properties and to the use of precision bore tubing the apparatus.
Aid to Music Composition Employing a Random Probability System
Authors: Olson Harry F. , Belar Herbert
Published: September 2005

The random probability system generates sequences of notes in a series which are not completely random nor completely ordered, but each note is selected in a random fashion with a probability which depends upon preceding notes. Combined with sound synthesizers, the machine provides additional instrumentation for the musical laboratory.
Notes on Scaling Jet and Rocket Noise
Authors: Bies David A. , Franken Peter A.
Published: September 2005

For dynamically similar systems it is shown that pressure fluctuation amplitudes at similar positions are the same when measured in constant percentage-frequency bands and when frequency is scaled inversely proportional to a characteristic length. This scaling relationship can be extended to systems containing acoustic liners if the linear flow resistance is held constant. Corrections for small errors in scaling are suggested for the case of rocket engines.
Remote Masking in Selected Frequency Regions
Authors: Deatherage Bruce H. , Bilger R. C. , Eldredge D. H.
Published: September 2005

Masked audiograms for six different masking stimuli were obtained from five observers. The audiograms show that remote masking can be controlled with respect to frequency region by controlling the envelope of the masking sound. Regular variations in the envelope at, say, 500 cps produce remote masking in the 500-cps region; while irregular, “random,” variations produce equal amounts of masking everywhere outside the frequency region corresponding to the masking band or tone. It is argued that the constant masking seen in remote masking is related to the fact that signal frequencies are differentially attenuated in their transmission from the tympanum to the cochlear partition, while the masking frequencies are not since they are actually generated at the cochlear partition itself.
On the Theory of the Propagation of Plane, Finite Amplitude Waves in a Dissipative Fluid
Authors: Lester William W.
Published: September 2005

The dissipationless theory for harmonic generation in an initially sinusoidal, plane, finite-amplitude wave is used as a basis for calculation of the harmonic components of such a wave in a fluid with dissipation. The assumption used is shown to lead approximately to the relationships of the Fox and Wallace theory. The result is given as a Fourier series, with graphs of the first few harmonic components for two specific cases. The series representation is valid for distances X⩽L, where L is the discontinuity distance for the dissipationless case.
Signal Detection as a Function of Signal Intensity and Duration
Authors: Green David M. , Birdsall Theodore G. , Tanner Wilson P.
Published: September 2005

The object of this study was to determine how signal amplitude and duration effect the detectability of a pure tone partially masked by random noise. If signal duration and amplitude are considered two dimensions in a space, the study attempted to determine the surface of detectability in this space. To accomplish this task three experiments were conducted with the same observers in each experiment. In the first experiment signal duration was held constant while amplitude was varied. In the second experiment signal energy was held constant while various pairs of values of signal duration and amplitude were tested. Finally, signal amplitude was held constant while signal duration was varied. A three parameter equation was determined which provided a reasonable fit to this surface of detectability in the plane of signal amplitude and duration. The equations are consistent with the data of previous research in this area. Finally, a comparison of the results and the predictions generated by a simple filter model is discussed.
Sound Propagation over Ocean Waters in Fog
Authors: Wiener Francis M.
Published: September 2005

Audible fog signals are extensively used as aids to marine navigation during periods of low visibility. Performance, however, has frequently been inadequate. To obtain better understanding of the physics of sound propagation over water in fog, a series of field experiments was carried out off the coast of Maine. Signals in the frequency range between about 200 and 2000 cps were employed to measure sound attenuation for distances up to a few miles. Simultaneous micrometeorological measurements were performed to describe the relevant properties of the lowest layers of the atmosphere through which the sound was propagated. This paper describes briefly the measurement techniques used and presents typical samples of the results obtained. Downwind, the average excess attenuation over and above inverse square law can be accounted for principally by molecular absorption. Upwind, large values of excess attenuation were found due to shadow zone formation. This constitutes a severe limitation of the useful range of audible fog signals. Fog itself contributes little to the average excess attenuation.
Interference Versus Frequency in Measurements in a Shallow Lake
Authors: Bobber Robert J.
Published: September 2005

When an omnidirectional projector and hydrophone are closely spaced and in shallow water, and sound is transmitted from one to the other, a large interference signal is superimposed on the direct signal. If the received signal is plotted as a function of frequency, as in a calibration measurement, the interference signal amplitude appears to be an inconsistent series of irregular sharp peaks and dips. A mathematical analysis of the condition where the transducers are midway between a water-air surface and a bubble-covered bottom shows that the shape, amplitude, and frequency of the interference pattern are predictable as the result of a large number of multireflection paths.
Application of the Theory of Signal Detectability to Amplitude Discrimination
Authors: Tanner Wilson P.
Published: September 2005

The fact that Weber's law appears to apply in the same way both to intensity discrimination for pure tones and to intensity discrimination for white noise poses a theoretical paradox: in the case of pure tones, the human observer becomes less efficient as the intensity of the tone is increased, while in the case of white noise he exhibits a constant efficiency independent of intensity.

An inventory of the various possible noise sources which may exist is made, and the way in which these may be expected to effect the detectability of a signal leads to the equation (d′)2=η2E&Dgr;NG+NE+kV02, where η is the individual observer's efficiency, NG is the noise introduced by the experimenter, NE is the uncontrolled noise present in the experimental situation, and k is a constant indicating that small amplitude variation in the oscillator constitutes a noise source proportional to the power of the lower of two signals to be discriminated.

Data for three observers over four noise levels is described by this equation sufficiently well to suggest that the hypothesis that Weber's law is merely a reflection of the oscillator noise (kV02) is plausible.
Performance of Magnetostrictive Transducers Made of Aluminum-Iron Alloy or Nickle-Copper Ferrite
Authors: Kikuchi Yoshimitsu
Published: September 2005

A brief history of the finding and development of aluminum-iron alloy introduces the description of our industrial specification as finally decided upon by the organized group. The description covers the specification for the melting and rolling processes, both of which are main factors affecting the magnetostriction characteristics. Improvement of transduction efficiency is then discussed in general, and it is concluded that no other material which has larger coupling factor than that of nickel, or “Alfer,” (i.e., the 13.5% aluminum-iron alloy), is necessary, in so far as the transducers to be used at their resonance are concerned. Improvement in the efficiency can be attained only by the considerable elimination of the eddy current, and this is accomplished by our several magnetostrictive transducers made of Ni-Cu ferrites which are shown to be excellent for generating underwater ultrasound. Electroacoustic efficiency is as high as 90% even at such higher frequencies as 70 and 100 kc. Intense generation of ultrasonic waves is successfully carried on up to the rate of 3 w/cm2 of the radiation surface.
Stepped Waveguide Transformers and Filters
Authors: Young Leo
Published: September 2005

A review of recent developments in the synthesis of stepped quarter-wave transformers and half-wave filters is given. A recent paper by Holte and Lambert is discussed.
Measurements with Ordinary Sound and Ultrasonics Carried Out in the Physical Laboratory of the University of Louvain
Authors: Van Itterbeek A.
Published: September 2005

This paper contains brief resumés of some of the acoustical research carried on at the University of Louvain during the year 1955–1956. Descriptions of apparatus and methods, and some interpretation of the results are given.
Inner Ear Response to High-Level Sounds
Authors: Lawrence Merle , Wolsk David , Schmidt Pieter
Published: September 2005

The cochlear ac potentials in response to a stimulating tone of rapidly increasing intensity undergo a rapid reduction in amplitude after reaching a certain maximum. The record seen on the cathode ray screen is indistinguishable from that reported for middle ear muscle action, yet the response described here occurs in the absence of muscles or of the entire middle ear. This effect is described as a “clamp,” but it is found to be the result of overloading in the inner ear. Within the limits of these experiments it is shown that the rate of rise of a tone makes no difference in the form of the cochlear ac response. This finding, if carried to extremes, would suggest that the inner ear behaves the same in the presence of impact noise as it does in the presence of steady-state or slowly rising tones.
Minimum Phase Responses for the Basilar Membrane
Authors: Flanagan James L. , Bird Carol M.
Published: September 2005

Appreciable experimental data exist for the amplitude of basilar membrane displacement as a function of sound frequency. Data on the phase of displacement vs frequency are relatively meager. At low frequencies the latter do not relate well to the phase predicted by recent mathematical models for membrane displacement. To examine the difference, we programmed a digital computer to calculate: (1) minimum phase functions corresponding to the experimental amplitude vs frequency responses; (2) inverse Fourier transforms of the experimental amplitude and phase data; and (3) inverse transforms of the experimental amplitude and calculated minimum phase data. The results were: (1) At low frequencies the calculated phase differs from the experimental phase by about 12π radians or more, with the membrane displacement leading that of the stapes. Constant delay (i.e., linear phase) does not account for the difference; (2) inverse transforms of the experimental data yield nonrealizable impulse responses, i.e., responses which are nonzero for negative times; and (3) inverse transforms of the experimental amplitude and calculated phase yield proper impulse responses. At low frequencies, therefore, the experimental amplitude and phase data do not seem completely compatible. For several reasons, the phase data seem more likely to include a small imprecision than do the amplitude data.
Effect of Time on Pitch Discrimination Thresholds under Several Psychophysical Procedures; Comparison with Intensity Discrimination Thresholds
Authors: König E.
Published: September 2005

This paper presents a study of the effect of the interstimulus interval on pitch discrimination the cases of five different psychophysical procedures. These procedures were approximately analogous to those employed by Pollack for intensity discrimination. All the experiments described here for pitch discrimination were carried out at a constant sound level of about 40 db above threshold, the mean reference frequency being 1000 cps. The listeners examined were five young men with normal hearing acuity between the ages of 20 and 30. From the experimental data it appears that, irrespective of the method used, the mean over-all performance of the subjects in pitch discrimination deteriorates only slightly as the interstimulus interval increases from 1.25 to 5 sec. In order to stress the large discrepancies among the performance of the listeners, the data for each subject were reported with special care. The effect of stimulus duration on pitch discrimination is briefly discussed.
Temporary Threshold Shift with Changing Duty Cycle
Authors: Selters Weldon , Ward W. Dixon
Published: September 2005

The empirical rule that interrupted noise having an on-fraction R produces R times the TTS that the same noise would produce if on continuously (the on-fraction rule) was tested for R≈0.5 and for various duty cycles from 1 min to 16 min. The TTS from the 1-min and 2-min duty cycles agreed with the value predicted by the rule, but the 4-min, 8-min, and 16-min duty cycles gave respectively 1.07, 1.21, and 1.29 times the R-based values. This result indicates that the on-fraction rule breaks down when on-off times exceed about 1 min, but that the rule may be extended for periodic or nearly periodic noises by incorporating correction factor based on the length of the period.
Perception of Vowels Heard in Noises of Various Spectra
Authors: Pickett J. M.
Published: September 2005

The perception of vowels heard in noises of various spectra is analyzed by means of stimulus-response matrices. The stimulus vowels were spoken in PB-word lists and in syllable lists in which the vowels were equally probable. The matrices show shifts in vowel confusions depending on how different noise spectra mask the vowel formants. Vowel duration and intensity are measured and related to vowel perception. Vowel guessing is related to past training.
Effects of Vocal Effort upon the Consonant-Vowel Ratio within the Syllable
Authors: Fairbanks Grant , Miron Murray S.
Published: September 2005

Subjects spoke /s/-vowel-/s/ monosyllables at two syllabic levels which required a large contrast in effort without extreme departure from average conversational effort. At the higher level the median within-syllable consonant-vowel ratio was approximately −14 db; at the lower level (vowel 18 db down) it was approximately −7 db. The ratio also varied with position of the consonant within the syllable, with vowel and with sex of speaker; effort, vowel, and sex interacted. The variations were systematic and large enough to have implications for intelligibility.
Role of Time Integration in the Discrimination of Frequency Response Patterns
Authors: Hunt F. V.
Published: September 2005

The hypothesis is advanced that a time-invariant pattern of frequency response can be discriminated in the presence of a variable pattern of frequency-response irregularity only when the listening interval is of sufficient duration to allow the variable part of the total response pattern to be averaged out. Qualitative evidence seems to support the hypothesis, but quantitative evaluation of the needed integration times is still wanting. If the effect is real, however, it may have an important bearing on the interpretation of the conventional A - B tests used for the assessment of sound reproducing systems.
Lateral Line in Fish—Possible Mode of Action
Authors: Suckling E. E.
Published: September 2005

The proposal is made that fish detect low-frequency sounds as “internal vibrations” rather than as direct oscillations of the water.
Acoustical Design of Modern German Organs
Authors: Lottermoser W.
Published: September 2005

Previous work on the acoustical qualities of several famous baroque organs, which is here reviewed, reveals two maxima in the spectra of the “plenum” sounds, one at lower frequency formed by the fundamentals and lower harmonics, and one at a higher frequency formed by the partial tones of the mixture stops having several ranks of pipes. In Germany where many organs were destroyed in the last war, organists and parishes want to get new instruments of the same or a similar sound quality as the famous baroque organs. If approached in the usual way, this goal is reached only by extraordinary effort and dexterity. It is possible by acoustical planning, however, to attain with accuracy the desired spectra in a relatively short time. Two characteristic examples of such research are described here: the Praetorius organ at Freiburg and the Choir organ of St. Mary's Cathedral at Lübeck. In the first case, room acoustics were planned to get the desired sound-energy distribution for the organ. In the second case, proposals for the diameters and the installation of the pipes were made to adapt the organ to the room acoustics, in order to reproduce the characteristic baroque sound spectra in the nave of the church.
Extensional Waves in Fluid-Saturated Porous Cylinders
Authors: Gardner G. H. F.
Published: September 2005

Pochhammer's method of analysis for waves in circular cylinders is extended to Biot's theory for an elastic porous solid saturated with a compressible viscous fluid. Attention is given mainly to slender rods vibrating at low frequencies. The boundary condition of zero stresses on the curved cylindrical surface is used to derive the frequency equation from which phase velocity and attenuation may be obtained. In general, two types of extensional waves exist, just as there are two types of dilatational waves. The attenuation per unit length of the first kind of wave is proportional to the square of the frequency at low frequencies except when the wavelength of dilatational waves of the second kind is about half the perimeter of the cylinder. In the neighborhood of this frequency the attenuation may show a maximum. Waves of the second kind behave like a diffusion phenomenon, except in the same neighborhood.
Basis for the Acoustical Study of Singing
Authors: Fry D. B. , Manén Lucie
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, (2) the mood which the singer expresses, and (3) the vowel which is articulated.

Preliminary experiments suggest that acoustic differences (apparent in spectrograms) may be found regularly correlated with the differences of voice, mood and articulation covered by the system of classification.
Isolation from Vibration with a Mounting Utilizing Low- and High-Damping Rubberlike Materials
Authors: Snowdon J. C.
Published: September 2005

The dynamic mechanical properties of rubberlike materials have been briefly reviewed. The value of a mounting composed of a low- and a high-damping rubber in parallel is in this way made apparent. Expressions have been derived from which the ability of the so-called parallel mounting to isolate vibration from any nonrigid foundation may be determined, if the mechanical impedance of the foundation is known.

One- and two-stage mounting systems have been considered. To compare their performance, the mechanical impedance of a damped beam has been employed to simulate the behavior of a nonrigid foundation. It is shown that the parallel mounting suppresses resonant motion at the natural frequencies of the foundation and the mounting systems with similar effectiveness to the high-damping rubber, yet provides the greater isolation at other frequencies. The isolation afforded by the mounting is, in fact, often comparable to that which the low-damping rubber affords.
Vibration Treatment of Metals
Authors: Seemann H. J. , Staats H.
Published: September 2005

The treatment of solid and liquid metals by elastic vibrations is discussed. Particular attention is paid to the electrodynamic method in which the alternating field of a coreless induction furnace has a strong static magnetic field superimposed on it, so that the molten metal under treatment, itself becomes the sonic transducer with the production of radially directed vibrations. An expression is derived for the acoustic efficiency of this arrangement. Various special designs are described.
Ultrasonic Propagation Measurement in Sea Water up to 400 kc
Authors: Hashimoto Tomiju , Kikuchi Yoshimitsu
Published: September 2005

The propagation characteristics of ultrasound in sea water and its ultrasonic reflection loss on the sea bottom or on fish schools must be studied for both the design and the practical operation of echo sounders, fish finders, and SONAR's. This paper shows a practical method for this study, together with the results of measured propagation characteristics in both vertical and horizontal directions, as well as the ultrasonic reflection loss on the sea bottom and on fish schools, using 28, 50, 200, 300, and 400 kc.

The propagation attenuation in a direction vertical to the sea surface is the result mainly of spherical divergence, but the attenuation in a horizontal direction is caused partly by absorption as well. This absorption becomes larger at higher frequencies: in fact, the results of experiments show that the absorption is 10–20 db/km at 28 kc, 37–50 db/km at 200 kc, and about 120. db/km at 400 kc. The reflection loss of the ultrasound at a fish school decreases as frequency increases. On the contrary, the reflection loss of the sea bottom increases as frequency increases. At 200 kc, therefore, the echoes from ground fishes sometimes become stronger than that from the sea bottom.
On the Fusion of Sounds Reaching Different Sense Organs
Authors: Broadbent D. E. , Ladefoged Peter
Published: September 2005

A simple place theory of hearing raises the problem that several mixed harmonics may be attributed by the listener to their appropriate fundamental frequencies: the recognition of a vowel sound in the presence of other sounds requires that the formants of the vowel be detected as such and not classified with the other sounds. Thus, the neural message from a particular part of the basilar membrane probably conveys in some way information on the fundamental frequency, to a harmonic of which that part of the membrane is responding. The problem of fusion of sounds on the two ears is merely an extension of the problem of fusion of different frequencies in one ear.

It is shown that synthetically produced speech will fuse when the first formant is presented to one ear and the second to the other, but it will not do so if the formants are given different fundamental frequencies. Even when both formants are given to the same ear, the latter condition fails to fuse. A further experiment with sustained formants shows that binaural fusion is not explained by the identity of some of the Fourier components on the two ears.
Acoustic Impedance of a Helmholtz Resonator at Very High Amplitude
Authors: Bies David A. , Wilson O. B.
Published: September 2005

The acoustic impedance of a Helmholtz resonator terminating a ten-inch diameter tube has been investigated for sound pressure levels in the resonator of from 100 db to 170 db and for a range of particle velocities in the neck of from 1.3 cm/sec to 1.2×104 cm/sec (rms). Two different mounting orientations showed the same general rise in acoustic resistance and rise in resonant frequency with increasing sound pressure level but gave quite different results in detail.
Sound Transmission through Thin Cylindrical Shells
Authors: Smith P. W.
Published: September 2005

An analysis presented of the impedance presented by a thin cylindrical elastic shell to a pressure or normal stress as a function of the axial wavelength and the angular dependence of the forces. Results of computation are presented graphically. This information is then used to compute a measure of the sound transmitted through the shell immersed in air for various particular cases. The theory of the scattering and absorption of waves incident upon a cylinder at angles other than normal is developed for this purpose. The results and their implications are discussed in detail.
Properties of the Eighth Nerve Action Potential
Authors: Ruben R. J. , Fisch U. , Hudson W.
Published: September 2005

The eighth nerve action potential in the cat was recorded from the round window and from the eighth nerve. The conduction velocity, measured directly and computed from the fiber diameter, was found to be approximately 25 m/sec. Comparison of the onset of the action potential at the round window and its appearance in the eighth nerve showed a delay of 0.3 msec, based upon the theoretical time of transmission according to the conduction velocity. As the stimulus intensity was increased, a decrease in the latency of the action potential of the eighth nerve was noted.
Propagation of Plane Sound Waves of Finite Amplitude in Nondissipative Fluids
Authors: Blackstock David T.
Published: September 2005

An extensive theoretical treatment is presented of the problem of plane progressive sound waves (simple waves) produced by continuous, high-amplitude motion of a piston in a lossless, semi-infinite tube. The fluid in the tube is assumed to be nondissipative; liquids as well as perfect gases are considered. The analysis is given in both Eulerian and Lagrangian coordinates. Earnshaw's exact solution in parametric form is first given for arbitrary piston motion. Special attention is then given to the case of sinusoidal piston motion. Approximate but explicit power- and Fourier-series solutions for this case are derived from the exact solution. A low-amplitude nonlinear theory of simple waves is proposed. In this theory nonlinear effects are considered in a simple yet general manner.

A brief analysis of shock formation is also given. It is shown that the generally accepted formula for the distance at which the shock forms when the piston motion is sinusoidal is rigorously correct only under very special circumstances.
Experimental Investigation of Conical Horns Used with Underwater Sound Transducers
Authors: Owens W. R. , McKinney C. M.
Published: September 2005

An experimental study has been made of radiation patterns and axial gain in the Fraunhofer region for conical horns used in conjunction with underwater sound transducers. Results of the data are presented in a form that is useful in design of conical horns that have optimum dimensions.
Radiation Impedance of a Cylindrical Bore in a Solid
Authors: White Richard M.
Published: September 2005

It is shown that for the appearance of a zero in the radiation reactance at the wall of a cavity in a solid the same restrictions on Poisson's ratio apply whether the cavity be spherical or circular cylindrical in shape.
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 principles of projecting sound 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 reverberent 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. The enhancement effect of reverberation on musical tones is shown to be related to the optimum reverberation characteristic. A new design of church auditorium is submitted which is interesting in its novelty, and is still 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. Space requirements for organs and some principles of organ design including the design of mixtures to meet any reasonable acoustic condition are given. 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.
Investigation of the Line-and-Cone Underwater Sound Transducer
Authors: Baird D. L. , McKinney C. M.
Published: September 2005

An experimental investigation has been made of a transducer-reflector combination consisting of a 90° conical reflector with a line transducer placed along the axis. Both far field and near-field data indicate that, except at low frequencies, when a uniform line is used, the radiation patterns are equivalent to those from a uniform circular aperture. Evidently other effects compensate for the geometrical shading. By a suitable choice of line-element connection, however, a shaded aperture distribution can be obtained. The horn reflector increases the sensitivity of the transducer but not to the extent predicted from the geometry. The interaction of elements composing the line transducer is increased by the addition of the conical reflector.
Surface Backscattering Strengths Measured with Explosive Sound Sources
Authors: Chapman R. P. , Harris J. H.
Published: September 2005

The scattering strength of the sea surface was measured for a range of wind velocities, grazing angles, and frequencies, in octave bands in the frequency range from 400 to 6400 cps. An empirical equation was obtained relating the scattering strength of the sea surface to the above variables, for grazing angles below 40°. At low grazing angles, scattering of sound from a subsurface layer of isotropic scatterers, probably of biological origin, frequently masked the reverberation due to scattering from surface roughness. For a given wind speed, the scattering strengths measured in this study at grazing angles below 20° were appreciably less than those obtained by other observers at higher frequencies. At higher grazing angles, of the order of 40°, there was little systematic difference between the measurements made at high and low frequencies.