bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Noise Correlation on Binaural-Signal Detection
Authors: Robinson Donald E. , Jeffress Lloyd A.
Published: September 2005

This is an extension of a study of the effect of the interaural correlation for a masking noise upon the masked threshold for a 500-cps tone as reported in 1961 by Robinson and Jeffress. At that time, comparisons were made between thresholds obtained under both homophasic and antiphasic conditions. However, the variability associated with the threshold measurements (obtained by the constant method) was such as to obscure possible differences between the two antiphasic conditions or between the two homophasic. The present study employs a method derived from the theory of signal detection to obtain a more stable measure of the effects of interaural-noise correlation. Performance was measured in a two-interval forced-choice experiment. The signal levels required for a predetermined value of d′ were obtained for the various conditions from functions relating d′ toE/No. Such signal levels, when plotted as masking level differences (MLD's) relative to the homophasic condition at the 1.0 value of the noise correlation, permit comparisons with similar data obtained by a threshold procedure. The results show, as did the results of the earlier study, a very rapid increase in masking as the correlation is reduced from unity for the antiphasic conditions and a gradual decrease in masking for the homophasic conditions with the same shift in correlation. In addition, the functions relating d′ to E/No show large differences in slope between the antiphasic and homophasic conditions.
Redefinition of Fundamental Frequency
Authors: Tikofsky R. S. , Perry P.
Published: September 2005

Fundamental frequency of normal and esophageal utterances was measured by (1) number of pulses in a spectrographic continuous-amplitude display, (2) number of cycles in an oscillographic wavetracing, (3) harmonic interval in a narrow-band spectrogram. The results obtained by these measures yield widely varying fundamental frequencies. Moreover, narrow-band spectrograms often show two fundamental frequencies. In the case of two fundamental frequencies, the width of the harmonic interval in the high frequencies is one-half the width appearing in the low frequencies. Defining fundamental frequency in terms of (1) the number of pulse groups, rather than the number of pulses, and (2) the smallest harmonic interval, brings all three methods into agreement. The appearance of pulses in amplitude and/or time groups suggests that a single glottal cycle in some instances may be best defined as extending through more than one opening and closing of the glottis. (This research was supported by a grant from the National Institutes of Health.)
Exploratory Study of Energy Dissipation at Aircraft Structural Joints
Authors: Ungar Eric E. , Gogos Creighton M.
Published: September 2005

Vibration-decay measurements were performed on a riveted and on a spot-welded joint taken from an actual aircraft. The effects of a number of joint modifications were investigated in an attempt to discover the primary energy-dissipation mechanisms. The damping observed was surprisingly linear. Spot welds, rivets, and tight bolts were found to produce very similar damping characteristics. Increased gross interface contact area, looser or fewer connectors, and the addition of low-viscosity lubricants or rubbery adhesives were observed to produce increased damping. Use of rigid adhesives resulted in decreased damping. It appears that energy dissipation is not associated with the structure in the immediate vicinity of rivets or other connectors. Reduced interface friction seems to result in increased energy dissipation, probably because it permits more relative motion over a larger portion of the interface area. (This work was supported in part by the Aeronautical Systems Division U. S. Air Force.)
Experimental Comparison of Fatigue Life of a Beaded Panel Exposed to Jet and Siren Sounds
Authors: Smith Preston W. , Malme Charles I.
Published: September 2005

Panels of one beaded design were fatigued with jet-noise excitation in the field; their lives ranged from less than about 104 up to 1.7×106 cycles. Laboratory fatigue tests on panels of the same design were made with a siren. In one set of laboratory tests, the sound-pressure level was constant; in the other, the level was cycled up and down according to a program designed to simulate the moderately long-time statistics of the jet-noise excitation. Predictions from laboratory data of the fatigue life with jet-noise excitation were made by various methods. Predictions by some methods compare well with the field data, with differences in noise level of about 1 db or less. (Research sponsored by Aeronautical Systems Division, Air Force Systems Command, U. S. Air Force.)
Sonic Load History Recorder. II. Design
Authors: Ball Jay H. , Noiseux Denis U. , Starr Edward A.
Published: September 2005

The realization of a compact instrument to measure the accumulated acoustic exposure of a flight vehicle is considered. The output data of the instrument should aid in the estimation of fatigue life. Design criteria are discussed, such as techniques for amplitude analysis, sampling, and accumulation of data in a directly readable and usable form. A specific design of a breadboard model of the Sonic Recorder is presented. [This work was supported under U. S. Air Force Contract No. AF 33(616)-7789.]
Comparability of Mechanical-Impedance Measurements
Authors: Belsheim R. O. , Remmers G. M.
Published: September 2005

Mechanical impedance is now being measured by a number of investigators. Since the equipment and procedures used vary considerably, some differences in measured impedances may be expected. The ASA Shock and Vibration Committee has initiated a program to obtain comparisons of impedances on “representative” structures, including several beams, as measured by various investigators. This paper gives preliminary progress of this program; considerations involved in experimental design and in establishing appropriate structures are discussed.
Quantitative Description of Non-Gaussian Random Signals
Authors: Himelblau Harry , West Ben
Published: September 2005

The amplitude statistics of a continuous random signal are often expressed by the probability density. If the signal is Gaussian or normal, the well-known exponential equation and bell-shaped curve define these statistics. If the signal is non-Gaussian, but does not deviate from the Gaussian by too large a margin, either the Gram-Charlier or the Edgeworth series may be used to describe the signal and the amount of nonnormality. The amount of nonnormality is expressed in terms of the third and fourth statistical moments utilized in these series, which are called skewness and kurtosis, respectively. In this paper, the abbreviated Gram-Charlier and Edgeworth series are used to determine the amplitude probability density and the corresponding probability distribution as functions of skewness and kurtosis. Graphical results supplement the equations.
Central Inhibition of Auditory Input Following Stimulation of the Oliveo Cochlear Bundle in Cat
Authors: Ruben R. J. , Sekula J.
Published: September 2005

The work of Galambos demonstrated that stimulation of the oliveo cochlear bundle would reduce the N1 and N2 response without any diminution of the cochlear potential. This work was repeated and Galambos' results were confirmed. In addition to the electrode placed on the round window, there were electrodes placed on the auditory cortex, in the medial geniculate, and in the inferior colliculus. Stimulation of the oliveo cochlear bundle at intensities which caused minimal or no diminution of the N1 and N2 completely abolished the cortical evoked potential. The medial geniculate was totally suppressed at stimulus levels which caused a moderate diminution of the N1-N2 response. The inferior colliculus evoked potential response could only be suppressed with almost total inhibition of the N1-N2 response. It is felt that this indicates that stimulation of the oliveo cochlear bundle may do one of two things. It may either inhibit a select group of haircells or neurons which then are primarily responsible for the cortical response, or it may exert an independent central inhibitory effect on the auditory evoked potentials.
Early Histologic Changes Produced by Kanamycin in the Inner Ear of Cats
Authors: Reddy John B. , Igarashi Makoto
Published: September 2005

To determine the site of early lesions in the organ of Corti in domestic cats, the following pilot study was undertaken histopathologically. Kanamycin was injected over a period of 16 days using a minimal total dosage of 1440 mg and a maximum total dosage of 9600 ms. No functional or electrophysiological experiments were performed. Vestibular symptoms were not observed. The standard perfusion-fixation procedures were used and the results obtained suggest that early changes in Corti's organ were confined to the base turn in the cochlea. Successively, the supporting cells, particularly the Claudius' cells, outer hair cells, inner hair cells, and ganglion cells are damaged in that order. Further investigation is now being conducted to confirm these observations; the knowledge obtained may be of value in clinical medicine, and may also be applied in basic investigation of the function of the cochlear end organ in research animals.
Lateral Line Organ of Fish: A Possible Key to the Hair Cell Problem
Authors: van Bergeijk Willem A. , Harris Gerard G.
Published: September 2005

The mechanics and physiology of the hair cells of the cochlea are very difficult to investigate for obvious technical reasons. The hair cells of the lateral line of fish are embryologically and morphologically very similar to the hair cells of the inner ear. The morphological similarity is so close, in fact, that it seems warranted to investigate the hypothesis that all these different hair cells behave physiologically in a similar way. The ear can be thought of as an invaginated lateral line organ with a middle ear of some kind attached to transform pressure waves into volume displacements. We find, however, differences as well as similarities. Morphologically, the lateral-line organ of the killifish shows a curious polarization: in an oval patch of supporting cells, a strip of hair cells is embedded along the major axis. Physiologically, the organ is directionally sensitive along this axis, too. One remarkable difference is that, although the cochlear microphonic over a wide intensity range is proportional to the oval window displacement, the lateral line microphonic shows a double frequency which is indicative of some type of rectification.
Evidence that the Lateral Line Organ Responds to Water Displacements
Authors: Harris Gerard G. , van Bergeijk Willem A.
Published: September 2005

In recent years, there has been controversy whether the lateral line is sensitive to water displacements or to sound. Sound in this context has usually been understood to be pressure variations due to compressional waves. These waves produce displacements too small to stimulate the lateral-line organ. The near-field effects of acoustical sources in water, however, often produce displacements which can stimulate the lateral line organ. Depending on the type of source used, the amplitudes of these water motions decrease as the square or cube of the distance from the source. The magnitude of microphonics from the lateral-line organ on the head of killifish decreases with distance from the acoustical source in a way which proves that they are sensitive to the near-field effects and, thus, to some function of water displacement.
Representation of Sounds by Responses of Single Units in the Eighth Nerve of the Bullfrog
Authors: Goldstein Moise H. , Frishkopf Lawrence S. , Geisler C. Daniel
Published: September 2005

Single-unit recordings from the eighth nerve of the bullfrog have revealed two strikingly different types of response activity. The type of unit most often encountered is maximally sensitive to tone bursts of frequency between 1000 and 1500 cps. This type of unit cannot be inhibited by acoustic stimuli. Its frequency sensitivity and its capacity to follow pulse stimuli are well matched to the spectral composition and pitch period of the bullfrog's croak, respectively. The second type of unit is inhibited by acoustic signals in the frequency range between 300 and 1000 cps. Some units belonging to this group are not excited by acoustic stimuli but respond to vibrational stimuli; some respond to both acoustic and vibrational stimuli; and some respond to acoustic stimuli alone. Units of this type which can be excited by sound are usually most sensitive to frequencies between 200 and 400 cps, but occasionally units most sensitive to frequencies between 700 and 900 cps have been encountered. There is evidence that both types of unit activity are recorded from primary neurons. Responses to clicks, tones, noise bursts, click trains, and frog croaks were studied.
Transient Cross-Sectional Strain and Stress Distributions in Longitudinally Loaded Cylindrical Bars
Authors: Jones O. E.
Published: September 2005

Axially symmetric cross-sectional strain and stress distributions in semi-infinite circular elastic rods subjected to pressure-step or velocity-impact loadings are studied by using the double-transform technique of Folk, Fox, Shook, and Curtis [J. Acoust. Soc. Am. 30, 552 (1958)]. Asymptotic solutions are obtained as functions of time, radius, and distance down the bar for the strains ezz,, err, eθθ, and erz, and for the stresses τzz, τrr, τθθ, and τrx. Previous solutions, which have been based either explicitly or implicitly on the assumption that plane sections remain plane, do not accurately predict the diameter changes observed experimentally by Miklowitz [in Proceedings of the Third U. S. National Congress of Applied Mechanics (ASME, New York, 1958), p. 215]. The present solutions predict the Miklowitz results and provide further insight into the dispersive lateral-inertia mechanism. For very large distances down the bar, the solutions for the head of the pulse approach those obtained on the assumption that plane sections remain plane. Also, previous solutions for the pressure-step and velocity-impact problems are equivalent. In the present study, it is shown that this is a first approximation; differences between the solutions appear in the higher-order terms. (This work was performed under the auspices of the U. S. Atomic Energy Commission.)
Theoretical Study of Symmetric Wave Propagation in a Semi-Infinite Elastic Isotropic Cylinder
Authors: Zemanek Joseph
Published: September 2005

The boundary conditions at the traction-free interface of a semi-infinite elastic cylinder can, with one exception, be satisfied exactly only if an infinite number of modes of propagation is considered. For the low-frequency range (diameter<wavelength), there exists only a single mode of propagation with a real propagation constant [the L(0,1) mode]; however, there is also an infinite number of modes of propagation with complex propagation constants. All of these modes are required to satisfy the boundary conditions. An approximate solution is found for the problem of the L(0,1) mode impinging on a traction-free interface by using only a finite number of modes of propagation. The reflection coefficient for the L(0,1) mode is given. The accompanying generation of higher-order modes with complex propagation constants is shown to cause high-amplitude end resonances at isolated frequencies. Results are given for approximations with 3, 5, 7, and 9 modes.
Experimental Investigation of Elastic Wave Propagation in an Aluminum Cylinder
Authors: Zemanek Joseph
Published: September 2005

The resonant-bar technique was used to measure the dispersion of waves corresponding to symmetric and first and second antisymmetric modes of propagation. Wavelength information was obtained by measuring the spacing of the nodes along the length of the cylinder. The results of these measurements are compared to curves computed from the Pochhammer-Chree theory. In general, deviation between experimental and theoretical dispersion curves is less than 0.2%. The reflection coefficient for the L(0,1) mode obtained in this manner is compared to an approximation based on the Pochhammer-Chree theory. Standing-wave patterns at resonant frequencies in the vicinity of the end resonance show the build-up of high-amplitude displacements near the end of the cylinder. The measurements extend into the range of two propagating modes. Standing-wave patterns obtained in this range show a spatial-beating phenomenon due to interference between the two modes of propagation.
Acoustic Signals from Sparks in Air
Authors: Wright Wayne M.
Published: September 2005

There has been much interest in the shock waves which are generated by sparks both in liquids and in gases, but little is known of the acoustic signal which follows an initial shock front. Direct conversion of rapid pressure changes in air to electrical signals has been made possible by the development of a high-frequency electrostatic microphone with a resonance frequency of about 500 kc/sec and a corresponding rise time of less than 1 μsec. The stiffness which leads to electroacoustic transduction is provided by the thin-air film between a 0.00025-in. Mylar diaphragm and a smooth brass-back electrode across which it is stretched; a thin coating of aluminum on the exposed surface of the plastic provides the second electrode for the capacitor. Studies have been conducted on the dependence of the waveforms of weak shock waves on spark energy (0.001–0.1 joule) and propagation distance (up to 40 cm). Overpressures as great as 3% have been detected with three-dimensional propagation. One observes an N wave, in which the indicated rise times of the two shock fronts are apparently limited even now by the microphone. The duration of the rarefaction phase remains about twice that of the initial condensation as both increase with distance and energy. (This work was supported in part by the Office of Naval Research.)
Experimental Study of High-Frequency Sound Propagation in a Randomly Inhomogeneous Medium
Authors: Stone R. G. , Mintzer D.
Published: September 2005

Laboratory experiments have been performed to determine the dependence of acoustic fluctuations on the parameters of the temperature microstructure of the transmitting medium (water). Results reported at the May 1961 meeting of the Society were shown to be in agreement with a theory developed by Mintzer [J. Acoust. Soc. Am. 25, 922 (1953)] for values of r/ka2>>1, where r is the range from source to receiver, k is the acoustic-wave number, and a is the correlation size of the inhomogeneities. Mintzer has shown that the wave-theory solution is identical with the ray-theory solution of Bergmann [Phys. Rev. 70, 486 (1946)], when r/ka2<<1. In this limit, the coefficient of variation V (fractional standard deviation) of a series of pulses is given by V∼α(r/a)3/2, where α is the rms index of refraction variation from unity. The experimental measurements of V as a function of range and frequency for r/ka2<<1 are presented and compared with the Bergmann solution. From acoustic data obtained in the ray and wave regions, values of a and α have been calculated. These values are compared with results obtained from microstructure measurements. (This work was supported by the Office of Naval Research.)
Probable Deviation Range in an Anechoic Room from the Values Given by the Inverse-Distance Law in Free Space
Authors: Diestel H. G.
Published: September 2005

The sound field in an anechoic room is not exactly the same as that in free space, for it can be divided into two distinct parts, the direct sound field of the source and the reverberant sound field. The probable deviations of the sound pressure in the room from the values given by the inverse-distance law in free space are considered by means of image statistics. The deviations at any point are dependent on the ratio of the energy density of the reverberant sound to the energy density of the direct sound. For all points in the room having the same ratio of energy densities, the magnitude of the probable deviations is the same. In case of a point source, the probable deviation range A is given by the approximate formula: A ≐ 40rRS−12 db, where r=distance from the source in m, R=sound-reflection factor of the boundaries of the room in percent, S=surface of the room in m2. The approximation holds only for the small deviation range A⩽±1 db; for a bigger deviation range, a diagram is given. For directional loudspeakers and microphones, the probable deviation range depends furthermore on its directivity factor.
Estimation of Structural Response to Reverberant Sound Fields
Authors: Maidanik Gideon , Lyon Richard H.
Published: September 2005

Further developments in a statistical method for estimating vibrational levels of ribbed panels are presented [R. H. Lyon and G. Maidanik, J. Acoust. Soc. Am. 33, 1668A (1961)]. Specifically, the radiation resistance of ribbed panels is analyzed as a function of frequency. It is shown that, below the coincidence frequency of the panel, the stringers and frames usually increase the radiation resistance of the panel and, hence, its coupling to the acoustic field. The results of experiments which were conducted to test the theory are reported. The agreement between theory and experiments appears to be satisfactory. (This work was supported by the National Aeronautics and Space Administration.)
Practical Problems in the Measurement of Reverberation Time
Authors: Schultz T. J.
Published: September 2005

The reverberation time of an occupied hall is of considerably more interest than that of an empty hall; yet, the practical difficulties of obtaining such data without unduly disturbing the audience are sufficiently great that reliable data for the occupied condition are comparatively rare. This paper discusses some commonly used methods of measurement of reverberation time of occupied spaces, such as observing the decay following sharp orchestral cutoffs during an actual performance and employing explosive excitation (pistol or cannon shots) of the hall. Measurement methods are suggested which appear to offer advantages over both of these.
Measurement of Sound-Transmission Loss in the Field
Authors: Farrell W. R. , Watters B. G.
Published: September 2005

Field transmission-loss measurements are an important part of architectural-acoustics work. The technical problems of making field measurements differ in many respects from the problems of laboratory measurements. These problems and some solutions are discussed.
Evaluation of Microphone Performance in a Field of Intense Nuclear Radiation
Authors: Manhart J. K.
Published: September 2005

Several types of commercial microphones and their related equipment have been tested in a nuclear reactor to determine the effect of intense nuclear radiation on their performance. In the past, microphones used to measure the sound field near the exhaust of a nuclear reactor have failed to perform satisfactorily due to high radiation levels. In order to obtain meaningful acoustical data during subsequent tests around a similar engine, an experimental study has been made to determine the performance of microphone assemblies while they were exposed to intense nuclear radiation. The subjects discussed in this paper include: (a) description of the test installation; (b) types of tests conducted; (c) types of failures observed in different kinds of microphones; (d) microphones used for this test are rated in the order of their sensitivity to nuclear radiation.
Errors in the Averaging of Logarithmic Estimators of Sound Pressures
Authors: Fox H. L.
Published: September 2005

An analysis of the intrinsic errors of a class of data-reduction techniques is presented. To obtain wide dynamic range, the logarithm of an incomplete average of a fluctuating quantity is obtained and then fully averaged. This is the process of reading a meter with a logarithmic scale or of estimating the mean value from a recording of fluctuations of the output of a level recorder. The visual averaging has been replaced in an instrumentation concept implemented by D. N. Keast. We present a mathematical analysis. It is shown that the intrinsic errors are a function of the input bandwidth, internal averaging time (that is, prior to taking the logarithm), and the type of detection used. (This work was supported in part by the George C. Marshall Space Flight Center, National Aeronautics and Space Administration.)
Pitch of Periodic Pulses with Nonuniform Amplitudes
Authors: Flanagan J. L. , Guttman Newman , Watson B. J.
Published: September 2005

Subjects, listening with ear-phones, adjusted the pitch of a uniform, periodic train of pulses to match the pitch of an experimental pulse pattern. One experimental pattern was periodic pulses with alternate amplitudes +a and +b. A second was similar but with alternate pulse amplitudes +a and −b. All pulse durations were 25 μsec. The parameters investigated, besides polarity pattern, were level difference ΔL=20 log |a/b| (0 to 20 db), and pulse rate (25 to 1074 pps). Results show that, roughly, for the (+a,+b) pattern a pulse-rate match is made for a ΔL less than 6 db, regardless of pulse rate. For ΔL greater than 10 db, a match of one-half pulse rate is made, also independent of pulse rate. For the (+a,−b) pattern, on the other hand, the pitch match is highly dependent both upon pulse rate and ΔL. As ΔL increases from 0 db, the match shifts away from the pulse rate at progressively lower frequencies. As in the first case, for ΔL>10 db, a pulse-rate match is never made. The amplitude and phase spectra of the stimuli are computed. The basilar-membrane displacements produced in the ear by the stimuli are simulated and examined. As in earlier experiments, the correlation between subjective behavior and membrane displacement is considered. Finally, the possible relationship of the results to the diplophonic voice is noted.
Auditory Pattern-Processing Model
Authors: Inomata Syuji
Published: September 2005

An auditory pattern-processing model has been proposed in which an input auditory signal is roughly processed initially by a bank of low-pass filters. Each filter output is fed to a probabilistic coder whose output pulse probability is a function of the average energy of the positive portion of the input signal. The circuits have three different modes of conversion. A special feature of the proposed model is that the “place pattern analysis” is done by a process similar to that of solving a Fredholm integral equation of the first kind, in which the kernel is related to the transmission characteristics of the low-pass filters. The spectrum reconstruction or spectral sharpening that can be achieved by this process is analogous in function to the sharpening observed in neurophysiological experiments. The time-pattern analysis, on the other hand, is carried out by periodicity-detecting methods. The relation of the model to psychoacoustical and neurophysiological data is discussed, and the implications of the model with regard to the specification of optimum speech-processing devices are considered. A programming method to implement the model on a digital computer is outlined. (This work was supported in part by the U. S. Army Signal Corps, the U. S. Air Force Office of Scientific Research, and the Office of Naval Research; and in part by the National Science Foundation.)
Surface Waves in Thin-Walled Air-Filled Cylinders in Water
Authors: Diercks K. J.
Published: September 2005

In a previous paper, evidence was presented for the existence of a surface wave making successive revolutions around the circumference of air-filled cylinders in water. Measurements showing the relation of the velocity of the wave to wall thickness and wavelength were displayed. For brass and aluminum cylindrical shells of 5.5 in. outside diam, but with varying wall thicknesses, the measured velocities fell along a curve for the velocity of plane longitudinal waves in plates for a Poisson's Ratio (σ) of 0.290, less than the σ's of brass or aluminum. The immediate implication was that the effective σ for a curved plate was less than that for a flat plate. To investigate this result further, and at the same time to study the influence of outside diameter on the behavior of surface waves. similar measurements of surface-wave velocity (and decay) in cylinders with 3.5, 8.5, and 12.0 in. outside diam have been made. There is again a decrease in the effective σ of the curved plates relative to flat plates as evidenced by the velocity curves. Data showing the simultaneous existence of a second vibrational mode have also been obtained.
Axial Vibrations of a Whirling Bar
Authors: Bhuta P. G.
Published: September 2005

Whirling bars have been used as antenna elements of artificial satellites. Axial vibrations of such bars are studied using undeformed coordinates. It is found that, in general, the effect of whirling is to lower the natural frequencies of the bars. For the static case, an interesting result, which has not been previously reported, is obtained as a special case of the dynamic problem. When the angular velocity of the bar approaches certain critical values, “static resonances” or instabilities occur and the axial displacements everywhere in the bar tend to become unboundedly large. These resonances are explained physically. The same problem is also worked out using final or deformed coordinates, and it is shown that the static resonances cannot come out of such an analysis. Moreover, the rotation does not have any affect on the natural frequencies when deformed coordinates are used. The results of the analysis using undeformed coordinates appear to be more compatible with the physics of the problem.
Preliminary Investigation of Echo Strengths Received from the Sea Floor
Authors: Breslau L. R. , Hersey J. B. , Hays E. E.
Published: September 2005

Sound-reflecting characteristics of the sea floor have been studied by means of a semiautomatic system for recording the peak pressure and the time integral of the square of the pressure of the bottom echo received by an Edo UQN-1b transducer operated at 12 kc. This system was used to record a detailed reflection profile across the Madeira Abyssal Plain during the fall of 1961. In addition, a self-contained pinger, employing a somewhat similar transducer, was lowered to the bottom in this area to measure bottom-echo levels and propagation loss. The nature of the sea floor as an acoustic reflector at 12 kc is discussed, based on the echo levels measured during the pinger lowering. The variation in the reflecting properties of the sea floor across the Madeira Abyssal Plain is discussed.
Rippled-Boundary Acoustic Experiment
Authors: Middleton F. H. , Yen N. C.
Published: September 2005

A ripple structure on a sandy ocean bottom produces important changes in the reflection characteristics of the boundary. This effect is analogous to the focusing produced by an optical-reflection grating. The acoustics problem has been studied since the time of Lord Rayleigh, with successes being limited to the case of extremely small corrugation amplitudes. This paper presents some results obtained from a model-tank experiment wherein a scale factor of about 20:1 is applied to the acoustic frequency and linear dimensions. The model boundaries were constructed of a plaster-sand mixture and of very fine sand in both flat and corrugated forms. In the experiments, the incidence angle was set while a complete semicircular reflection pattern was recorded for the whole region above the sonified boundary section. The incidence angle was varied from grazing to normal, so that families of reflection patterns were produced for the flat and corrugated-plaster and for the flat and corrugated-sand boundaries. These patterns are shown in the paper, as well as some curves showing the specular and backscatter [toward the sound source] amplitude dependence upon incidence angle and boundary contour. The experimental work is still in progress.
Component Gestures in the Production of Oral and Nasal Labial Stops
Authors: Harris Katherine S. , Schvey Malcolm M. , Lysaught Gloria F.
Published: September 2005

A previous study [G. F. Lysaught, R. J. Rosov, and K. S. Harris, J. Acoust. Soc. Am. 33, 842 (1961)] showed that although the glottis behaves differently for the oral labial stops /p/ and /b/, there is no significant difference between them in the pattern of electromyographic activity at the lips. In the present study, we found that /m/ has the same pattern of lip action. Furthermore, we were able to analyze the action of the musculature of the soft palate in the articulation of these three sounds. For the nasal /m/, no activity was observed anywhere in the palatal region. For /p/ or /b/, however, there is an identical burst of activity which can be measured on either superior or inferior palatal surface. The shape of the electromyographic pattern changes depending on whether the /p/ or /b/ follows a nasal or another oral sound, but changes in the same way for /p/ and /b/. The findings of these studies suggest a simple picture of the independent action of the various parts of the articulatory apparatus, which parallels the results of perceptual studies.
Spectral Analysis of Fricative Consonants
Authors: Miller Joan E. , Mathews Max V. , Hughes George W.
Published: September 2005

The voiced and unvoiced fricatives /ȝ/, /z/, /v/ and /∫/, /s/, /ɾ/ were recorded in the context of /hɔ′/ /fricative/ /vowel/ /fricative/ for nine vowels and seven speakers—four male and three female. Estimates of the fricative spectra were obtained by taking the Fourier transform of the autocorrelation function of the pressure wave. An error analysis was carried out to show what compromise between bandwidth and accuracy is necessary to observe spectral features. In particular, averaging times of the order of 50 msec and bandwidths of the order of 400 cycles are required for accuracies of about ±1 db in the spectral amplitude. These accuracies make doubtful the separation of spectral features closer than about 400 cycles or the detection of movements of these features occurring in less than 50 msec. Thus, the fricatives must be characterized for analysis purposes by fairly gross features. The average amplitude and first three moments of the spectrum were computed and their variance studied as a function of fricative position (medial or terminal), speaker, and vowel context. In addition, the spectra were fitted with various combinations of poles and zeros.
Vowel Duration in an Artificial Talker Driven from a Phonetic Input
Authors: Gerstman Louis J.
Published: September 2005

At the 1961 Spring Meeting of the Society, we described a computer program which accepts for its input the names of phonemes punched on IBM cards and produces as its output the acoustic waveforms of connected speech. The program considers each phoneme to be composed of a context-free steady-state portion, together with initial and final transitions whose courses are determined by the identities of the phonemes on either side. Nominal steady-state and transition durations are stored for each phoneme, but, in actual practice, to produce natural phrasing the vowel durations have had to be adjusted by means of additional entries on the input cards. That situation has now been improved through a revision of the program whereby each vowel is stored in both stressed and unstressed forms, the desired version being signaled by a diacritic (/) in the input code. Remaining occasions necessitating the adjustment of stored times appear to reflect the workings of sentence stress.
Jet-Engine Exhaust Noise—A Measure of Thrust
Authors: Duda John , Oran Frederic M.
Published: September 2005

The thrust of the jet engine is theoretically shown to be related to the over-all sound pressure of the jet exhaust regardless of environmental conditions. Within the range of tolerances required to measure thrust accurately on a competitive basis with existing systems, it is found that over-all sound-pressure-level measurements are not satisfactory. Numerous experiments have indicated that specific frequency regions of sound can be utilized to determine a correlation between sound and thrust. An instrument, the Jet Thrust Indicator (JTD), is described as having special filters such that the sound-pressure level of the frequency ranges correlates with thrust. The JTD provides direct readout in pounds of thrust. Actual field-test data are provided for aircraft and test stand-mounted jet engines. Thrust-measurement comparisons are made of the JTD with the conventional thrust-measuring techniques presently employed. Data obtained from field tests conducted over a wide range of atmospheric conditions and with various engines are reviewed. Results of the test program indicate an average accuracy of 2%. Applications including measurement of jet-engine thrust for ground check out on test stands and aircraft, go/no-go indications, and other uses are discussed.
Acoustic Trauma: Threshold Shifts and Recovery Patterns in the Cat
Authors: Beatty Dana
Published: September 2005

Cats previously trained to respond to tones at threshold (shuttle-box technique) were exposed to sound which produced varying degrees of temporary threshold shift (TTS) and permanent threshold shift (PTS). Exposure frequencies between 1 and 32 kc were employed. Threshold testing was begun from 1 to 24 hr posttrauma and continued at frequent intervals for from 2 to 10 weeks thereafter. In general, the results from 30 such exposures indicate that, following exposures of from 1 to 4 kc, the cats presented audiogram configurations similar to those obtained in man, and the TTS showed a recovery rate comparable to that of the human. Thresholds usually returned to pre-exposure levels following depressions of (1) 80 db or less (measured 1 hr posttrauma), or (2) 50 db or less (measured 24 hr posttrauma). Posttrauma recovery following high-frequency exposures was often characterized by unexpected and unusual depressions of acuity occurring from several days to 2 weeks after the exposure, in contrast to the recovery pattern observed following low-frequency exposures.
Auditory Fatigue and Changes in Audiometer Pen-Excursion Size
Authors: Silbiger Herman R. , Elliott Donald N.
Published: September 2005

Various investigators have reported changes in the size of pen excursions of a Békésy-type audiometer as a result of auditory fatigue. In individuals with perceptive losses, abnormally small pen excursions have often been interpreted as a sign of recruitment. Methodological factors, however, have sometimes been found to affect pen-excursion size. In the present study, the effects of (1) rate of attenuation, (2) type of test tone, and (3) SL of fatiguing tone on the size of pen excursions were studied. The results showed that both rate of attenuation and type of tone affected the size of pen excursions before exposure to the fatiguing tone. After exposure, the pen excursions became smaller under the more severe fatigue for the continuous tone only. A subsequent study then investigated the effect of type of tone (pulse or continuous) only, holding level of fatiguing tone and rate of attenuation constant, with each subject receiving both types of test tones. It was generally confirmed that continuous tones will result in decreases in size of pen excursions after fatigue, while pulse tones will not.
Bone-Conduction Thresholds for Sonic and Ultrasonic Frequencies
Authors: Oda Fujio , Corso John F.
Published: September 2005

Several investigators have reported that high-intensity sounds in the ultrasonic region above 20 kc can produce auditory sensations in individuals with normal hearing. The present experiment was performed to establish bone-conduction thresholds for pure tones from 5 to 100 kc in a group of subjects with no otological abnormalities. Fifty male and fifty female subjects, ranging in age from 18 to 24 years, were tested on only the left or right ear by a modified method of limits, with all tests being conducted in an anechoic chamber. A crystal transducer, calibrated in a water medium, was used to transmit the acoustic energy to the mastoid bone. The curve for the mean threshold of hearing (for subjects audiometrically screened by air conduction from 250 to 8000 cps) showed a very sharp rise between 10 and 20 kc with a slope of approximately 50 db/octave, and a gradual rise above 20 to 100 kc with a slope of approximately 18 db/octave. The maximal discrepancy between men and women was approximately 5.5 db (at 14 kc). In general, the results of the present study are in agreement with earlier fragmentary reports, e.g., mean threshold sound pressures of 40 db re 1 μbar at 20 kc and 78 db at 95 kc. (This research was supported by the National Institute of Neurological Diseases and Blindness, National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare.)
Microchronomatic Segmentation: A Phonetics Technique Applied to Heart-Sound Analysis
Authors: Truby H. M.
Published: September 2005

A mechanical segmentation method, developed originally for the purpose of permitting auditive discriminations along the time axis among posited speech events in rapid or tight phonetic sequences, is here applied to cardiographic and cardiologic analysis. The identification of acoustic elements per se (i.e., devoid of reference to such as linguistic criteria) is discussed. In an aspect of these regards, tape recordings and permanent oscillograms of a single heart-cycle are offered in demonstration of a tape-segmentation technique applicable to heart-sound analysis and especially applicable in the analysis of phasically complex heart-sound continua. In short, auscultation in general and the visual inspection of phonocardiograms in particular are elucidated by isolating and regrouping discrete intensity elements of such rapid-sequence phenomena as so-called “split heart-sound” and the like. The permanent tape recording itself is an invaluable supplement to phonocardiographic analysis, permitting review through repetitive listening and fostering more enlightened consultation. The inspection of heart-sounds, once permanently recorded, is further augmented through the isolation on magnetic tape of given short-time segments. Desired sequences may then be contrived and repeated for audition, for example, an isolated segment may be flanked by relative silence or placed differentially in relationship to its original acoustic environment as either the final or the initial element in the contrived sequence or augmented in various ways designed to facilitate its identification. Application of the suggested technique results in increased perceptual acuity on the part of the investigator and subsequent auxiliary analysis criteria.
Investigation of the Transmission of Ultrasound across an Interface under Pressure
Authors: Fehr Robert O.
Published: September 2005

An investigation was conducted to determine the effect of a normal pressure on the transmission of ultrasound across an interface. The results are presented.
Simultaneous vs Successive Observation Intervals in Signal Detection
Authors: Pfafflin S. M.
Published: September 2005

Performance in a two-interval forced-choice signal detection experiment employing simultaneous presentation of the observation intervals was compared with the performance obtained when the observation intervals occurred successively in time. In the simultaneous condition, two independent samples of random noise, one of which contained a sinusoidal signal, were introduced into the observer's earphones at the same time, one sample to each ear. The observer's task was to indicate into which of his ears the signal had been introduced. In the successive observation condition, the bursts of noise were separated by a short time interval and the observer was to indicate whether the first or the second burst contained the signal. Detection under the two methods of presentation varied for different subjects and signal parameters, but, in general, performance during simultaneous presentation was inferior to that obtained during successive presentation. Although a gain in detectability might have been expected to result from the opportunity for direct stimulus comparison provided by the simultaneous method, these data show that any such gain is more than offset by the introduction of factors detrimental to detection.
Comparisons of Some Statistical Distance Measures for Talker Identification
Authors: Becker M. H. , Gnanadesikan R. , Mathews M. V. , Pinkham R. S. , Pruzansky S. , Wilk M. B.
Published: September 2005

Preliminary results are given on a comparative study of various objective talker-recognition procedures, based on spectrographic analysis of 7 replicate utterances of each of 10 words by each of 10 different speakers. The spectrograms are quantized into 17 frequency channels and approximately 50 time channels. Different summarizations are applied to the spectrograms, including marginal energies, totalled across time, in each frequency channel; marginal energies for each time channel; and momentlike descriptions of energy distribution of the time margin. Various combinations of these summarizations were used as inputs to different multivariate distance measures, including (a) distance from unknown to a speaker centroid, using a metric based on a covariance matrix pooled over all speakers; (b) distances based on eigenvectors, using a classical discriminant-analysis approach; (c) distances based on metrics, employing individual speaker covariance matrices. Percent correct identification varied from 22% (discriminant analysis, using one eigenvector of energy margin on time) to 97% [distance (a) applied to the frequency margins]. Frequency classification of energy is better than time classification; distance (a) is better than the others; certain words are much better than others.
Speech Communications as Limited by Ambient Noise
Authors: Webster J. C.
Published: September 2005

Speech-intelligibility scores as a function of noise level are studied for face-to-face, sound-powered-phone, and amplified-speech- (earphone and loudspeaker) communication conditions. The speech-interference level (SIL) for octaves of noise centered at 500, 1000, and 2000 cps (0.5/1/2) is used as the measure of noise level. By using this noise measure, much of the work in this field can be brought together and interpreted. It is noted that “noisy” and “very noisy” spaces are associated with SIL's such that “shouting” or “very loud” voice levels (or 95-dB speech levels) are required for conversations at 1.5 or 3 ft, and this is the region where telephone conversations are judged to be “difficult” or “unsatisfactory.” All of these adverse noise conditions occur at the region where ear protection will aid intelligibility and at the boundary where ear protection should be used to protect against hearing losses. Where people must converse or communicate via some interior communication device (0.5/1/2), SIL's above 70 dB should be avoided. At levels greater than 90 dB (0.5/1/2) SIL, the wearing of hearing protection should be mandatory and every noiseproofing technique (except a noise shield for the microphone) should be employed. At levels above 100 dB SIL, every noiseproofing technique should be employed.
Analysis of Liquid Consonants
Authors: Kato Yasuo
Published: September 2005

A number of CVC syllables containing the liquids /l/ and /r/, and produced by three American English talkers, have been analyzed using analysis-by-synthesis methods. The temporal variation of the lowest three formants was measured throughout the utterances. In the case of /l/, the frequencies of a zero and a pole in the vicinity of the third formant were also measured as a function of time. This pole-zero-pole cluster for /l/ varied considerably with talker and with vowel context, but values of F1 and F2 showed less variation with talker. Transitions examined in an F1-F2 plane for both liquid consonants exhibited similar topological features for all talkers. Physiological interpretations of these data are discussed briefly.