bluuebunny/crossref_metadata_2025 huggingface dataset:
Reaction Time during the Discrimination of Synthetic Stop Consonants
Authors: Studdert-Kennedy M. , Liberman A. M. , Stevens Kenneth N.
Published: September 2005

The purpose was to determine how quickly and accurately listeners could discriminate between pairs of synthetic stop consonants distributed along an acoustic continuum. The stimuli, synthesized on OVE II at the Royal Institute of Technology, Stockholm, were 13 consonant-vowel syllables in which the second- and third-formant transitions varied so as to produce /b,d,g/. Stimuli were presented in ABX format and listeners responded by pressing a button. Reaction time was measured from the onset of the third member of each stimulus triad to the onset of the response. The percentage of correct discriminations rose to a peak in the vicinity of the phoneme boundaries, while reaction times fell. These results contrast with those of a previous study on the identification of the same stimuli: in that study, consistency of identification fell in the vicinity of the phoneme boundaries, while reaction times rose. Some implications for an understanding of the processes of identification and discrimination are discussed. [This study supported in part by the National Science Foundation.]
Crosslinguistic Study of Vowel Discrimination
Authors: Stevens Kenneth N. , Öhman S. E. G. , Studdert-Kennedy M. , Liberman A. M.
Published: September 2005

The objective of this experiment is to compare the identification and discrimination of a series of rounded and unrounded vowels by Swedish and American English listeners. All stimuli were produced with the OVE II synthesizer at the Royal Institute of Technology in Stockholm. The unrounded vowels are in the phonemic system of both Swedish and American English, and encompass the three vowels /i/, /ɪ/, and /ɛ/. The rounded vowels encompass the Swedish vowels /i/, /y/, /u/, but are not in the phonemic system of American English. Each series consists of 13 vowels, for which the first three formant frequencies vary in approximately equal logarithmic steps through the indicated range. By discrimination tests showed that both series of vowels gave essentially identical discrimination data for both groups of listeners. Identification functions for the unrounded vowels were similar for the two groups of listeners, but American English listeners were less consistent than Swedish listeners in the identification of the rounded vowels. Implications of the results with regard to theories of speech perception are discussed. [This study supported in part by the National Science Foundation.]
Application of Multichannel Processing to Analysis of Long-Range Refraction Seismograms
Authors: Hofmann Renner B. , Laster Stanley J.
Published: September 2005

Detailed interpretation of seismograms is dependent on the ability to decompose approximately the seismic disturbance into a set of events that have a simple theoretical basis. In the present paper, long-range refraction propagation is considered in terms of geometrical ray theory. The various rays possible in a typical model differ only slightly in frequency content and arrival time, but differ substantially in horizontal (phase) velocity. Individual later-arriving events can only rarely be identified on the conventional seismogram. Use of the frequency-wavenumber description of an event for processing on a multichannel basis allows identification and separation of the desired arrivals, with suppression of other arrivals. Examples are given of the application of such processing to two nuclear events recorded on the cross array at Tonto Forest Observatory (TFO), Arizona. The outputs of the array are combined in such a manner as to enhance successively lower velocities. The resulting “seismograms” may be considered 3-dimensional plots of amplitude versus velocity and arrival time. The PN and PG events are well-defined. There are indications of P* for at least one of the two events. Scattered (low-velocity) energy is negligible immediately after the arrival of PN, but is quite strong after PG. A likely scattering center is the sedimentary ridge north of TFO. The shear wave SG is also identified, and shown to be primarily transverse horizontal (SH). Theoretical computations are presented for the amplitudes of the various events, and the degree of similarity between theory and experiment is taken as a measure of our knowledge of the correct crustal structure.
Transmission of High-Frequency Acoustic Waves through an Absorbing Plate Immersed in Fluid
Authors: Crawford G. J. B.
Published: September 2005

An interferometric method has been employed in two ways to study the attenuation constants associated with compressional and shear waves. A “two-faced” transmitter (at frequencies above 400 kc/sec) and two identical receivers (each equidistant from, and on opposite sides of, the transmitter), whose resonant frequency is well above that used to power the source, are the essential acoustic elements. The driving force is a pulsed sine wave of long enough duration to establish “steady-state” conditions in the plate and yet avoid unwanted reflections. In the first arrangement (using one plate), the decreasing amplitude maxima of the transmission coefficient versus frequency are used to deduce the relation between attenuation and frequency. At frequencies (or thicknesses) where the transmission plot is exponential, two plates of different thicknesses are used to determine the attentuation constants directly. The reflection coefficients never enter the computations implicitly. The shear waves are “isolated” by properly choosing the incident angle. The various experimental limitations that have to be met are discussed briefly, together with some experimental results.
Transient Response of a Layered Medium with Tilted Interfaces
Authors: Sharma Darbari L.
Published: September 2005

The 2-dimensional problem of transient-wave propagation in a layered, fluid, or solid half-space with dipping interfaces is investigated to determine the effect of small tilt on reflected arrivals. The “ray-theory” technique is used to obtain these expressions caused by an impulsive line load at the surface. The geometry of the medium is introduced into the analysis by rotating the coordinate axes in the physical space, which necessitates a change in the spatial transform variable. Numerical results are presented for some typical examples.
Reflections from Lossy Media
Authors: White J. E.
Published: September 2005

A simple analysis shows that, when a transient plane wave in an elastic medium is reflected at a plane boundary with a lossy medium, the transient waveform of the reflection is affected by the loss parameters of the second medium. If the attenuation in the second medium is small and if the ρc products of the two media are matched, then the reflected waveform is the convolution of the incident waveform with the integral of the Fourier transform of attenuation as a function of frequency. Thus, attenuation for a lossy solid or liquid can be obtained by this external-pulse technique. Where attenuation is some simple function of frequency, its Fourier transform is some recognized generalized function. Sample waveforms have been observed, using airborne sound in specially prepared tubes.
Sound Propagation from High-Altitude Explosions
Authors: Diamond Marvin , Lee R. P.
Published: September 2005

Sound waves from a number of low-energy explosions at altitudes between 175 000 and 330 000 ft were detected by a square microphone array. The sound waves were incident on the earth's surface at angles between 60 and 86 deg. The altitude of the explosion as calculated by ray-tracing techniques agreed within 1% with the radar altitude. Frequency spectra of the detected N waves are presented. The mean wind velocity between 60–95 km was determined from the known source location and the azimuth of the detected sound wave.
Theoretical and Obtained ROC Curves for Antiphasic Stimulation
Authors: Jeffress Lloyd A. , Watson Charles S. , Rilling Mark E. , Bourbon Walter T.
Published: September 2005

The ROC curves of the previous paper [C. S. Watson, M. E. Rilling, and W.T. Bourbon. Paper D2, this meeting] for the diotic stimulus condition can be fitted closely by theoretical curves derived from amplitude distributions for noise and noise plus signal. The ROC curves for the antiphasic condition N0Sπ cannot; nor can they be fitted by theoretical curves derived from normal distributions. They can, however, be fitted reasonably well by theoretical curves based on the idea that the stimulus, now, is interaural time difference, that the noise is neural “noise” resulting from time uncertainty of neural firing, and that the signal is the interaural time difference that results from adding the tonal signal antiphasically to narrow-band, acoustic noise. [Work supported by USN Bureau of Ships contract NObsr-72627 and under a grant from the National Aeronautics and Space Administration R-129 through ONR contract 3579(04).]
Detection of Lateral Movement under Antiphasic Masking Conditions
Authors: Hafter Ervin R. , Bourbon Walter T. , Blocklr Anne S. , Tucker Ann
Published: September 2005

In a discussion of binaural phenomena of masking, Jeffress, Blodgett, Sandel, and Wood [J. Acoust. Soc. Am. 28, 416 (1956)] suggested that detection under the antiphasic condition N0Sπ results because the noise plus signal moves from the median plane previously occupied by the noise. The direction of the movement is random, but the amount of movement depends upon the amplitude of the signal relative to the noise. In the present study, listeners were presented with gated, 500-cps tones, 180° out of phase at the ears, in the presence of a continuous diotic noise, and asked to indicate the lateral displacement of the resulting stimulus. Distributions of their lateralization responses were obtained for several signal levels and showed reasonably good agreement with prediction. [Work supported by USN Bureau of Ships contract NObsr-72627 and under a grant from the National Aeronautics and Space Administration R-129 through ONR contract 3579(04).]
Binaural Masking—The Effects of Interaural Delay of the Noise on the Detection of Tones
Authors: Rabiner Lawrence R.
Published: September 2005

The purpose of this work was to examine the effects of interaural time delay of the noise on the detection of tones. The noise was 1200-cps bandwidth, white, Gaussian noise at a noise spectrum level of 57 dB/cycle (re 0.0002 dyn/cm2). The noise level was the same in both ears and identical tones were presented to the two ears. The tone frequencies included 1040, 694, 500, 297, and 167 cps. The method used to measure masked thresholds was a modified Békésy technique in which the listener approached threshold from a condition where there was always signal present to use as a basis of judgment. The results of this experiment support previously reported results of Jeffress, Blodgett, and Deatherage. The curve of binaural masking-level differences (BMLD) versus noise time delay (τn) shows cyclic behavior with a period identical to the period of the masked tone. These cycles are damped in that the maxima of the BMLD's decrease as τn, increases. The data at 297 and 167 cps indicate that the cycles flatten at low frequencies—the flattening first showing up at some frequency between 300 and 500 cps. Further results show that the flattening for low-frequency tones begins at about 0.8 msec and the BMLD remains constant until a relatively long time later, at which point it decreases.
Threshold Shifts for Continuous or Pulsed Tones Produced by Contralateral Steady or Pulsed Noise
Authors: Dirks Donald D. , Malmquist Carolyn
Published: September 2005

Threshold shifts for either constant or pulsed pure tones were observed while a steady or pulsed narrow band of noise was delivered to the contralateral ear via an insert receiver. By means of an internal control circuit, the electronic switch channels for the pure tone and noise could pass stimuli continuously or pulsed at a switching rate of 1000 msec, with a rise-decay time of 50 msec. Thus, 12 subjects were tested during five experimental conditions: (1) continuous tone and continuous masker; (2) continuous tone and pulsed masker; (3), (4) pulsed-pulsed, simultaneously and alternating; and (5) pulsed tone and continuous masker. The masking was always a narrow band of noise centered around 4000 cps and presented at levels of 50, 70, and 90 dB SPL. Thresholds at 4000, 1000, or 250 cps were recorded via a graphic attenuator. The results show that greater contralateral masking occurs when the masker and tone are pulsed simultaneously than in the condition where the noise is steady and the tone pulsed. [Research supported by grant NB 04019 from the National Institutes of Health, U. S. Department of Health, Education, and Welfare.]
Diffraction and Interaural Delay of a Progressive Sound Wave Caused by the Human Head
Authors: Bauer B. B. , Torick E.
Published: September 2005

A number of years ago Wiener [J. Acoust. Soc. Am. 19, 143–146 (1947)] published a paper on head diffraction; however, his data were limited to 6000 cps and did not include interaural delays. The present set of measurement extends to 10 000 cps, includes interaural delays, and covers a larger number of angles of incidence than explored by Wiener. The results can be applied to the design of high-quality earphones and to development of directional perception apparatus.
Effect of Geometry on Monostatic Scattering from the Ocean Bottom
Authors: Hurdle Burton G. , Flowers Kenneth D.
Published: September 2005

Monostatic bottom-scattering experiments were conducted in the Blake Plateau area with a piston transducer operated at 19.5 kc/sec and having a beam width of approximately 8 deg at the half-power points. This investigation was made to determine the degree of correspondence between measured returns and a model predicted by the theory of isotropic scattering from a boundary. Measured intensities were averaged and compared with the computed product of area and incident intensity as a function of time. These comparisons are made for grazing angles between 15 and 90 deg, and for pulse lengths of 2 to 3000 msec. The measured and computed curves were found to be essentially congruent for the range of grazing angles and pulse lengths employed. However, for a given grazing angle, it was found that scattering strength, the acoustic constant used to characterize the boundary, varied with the pulse length. This indicates that the scattering model has to be modified to be applicable in this case. The possibility of a modification based on energy scattered from within the bottom is discussed.
Quantitative Measure of the Acoustical Properties Of the Ocean Subbottom, Using Continuous Seismic-Profiling Data
Authors: Caulfield David D. , Bronson Gary J.
Published: September 2005

The continuous seismic-profiling system now in use at the Woods Hole Oceanographic Institution employs an electrical-spark sound source with a maximum stored energy of 100 000 J, a receiving system consisting of a streamlined, neutrally buoyant line-hydrophone array and associated amplifiers having a bandpass of 20 to 10 000 cps, and a high-quality tape recorder. When these received seismic signals are processed by a matched-filter detector and displayed on a precision graphic recorder (PGR), an accurate quantitative measure of travel time through the subbottoms and a clear, qualitative picture of these layers results. It is now possible to obtain a quantitative measure of the reflectivity and absorption characteristics of the subbottom and bottom layers in the frequency ranges of 20–1000 cps. The received signals are first converted from analog to digital format and then processed through a series of digital-computer programs: statistical techniques that improve signal-to-noise ratio, Fourier analysis, filtering, matched-filter detection, and programs relating measured spectrum to original source spectrum. The detailed frequency and phase measurements of the information thus obtained allow new interpretations to be made of the substructures and give new acoustical signatures to the substrata. Results of data taken southeast of New England on the Continental Rise show that the energy spectrum of the first bottom reflection can be used to determine the original source depth to within 1-ft accuracy. The original source spectrum including surface reflections can be determined to an accuracy of 3%. Knowing the source spectrum, the reflectivity and absorption coefficients for the bottom and of each subbottom have been computed as a function of frequency for the above area.
Energy Dissipation during Impact
Authors: Ripperger E. A.
Published: September 2005

Protection of equipment during impact requires a cushioning system that will limit accelerations to some predetermined level. In general, such cushioning systems must be capable of dissipating a large amount of energy per unit weight of the system. This capability requires that some very special characteristics in the systems be employed. These characteristics are discussed and illustrations are given of materials and systems that have these characteristics; special advantages and disadvantages that various systems have are pointed out. Methods for evaluating cushioning systems are discussed and typical force-displacement curves are shown. Costs per ft⋅lb of energy dissipated are compared for certain selected systems. Latest developments in energy-dissipation techniques are discussed and most likely areas of future development are suggested.
Interaction between a Spacecraft and Soil during Impact
Authors: Reese Lymon C.
Published: September 2005

In future flights of manned spacecraft, it may be desirable to land the spacecraft on soil rather than on water. A landing on soil would introduce many problems. The problem discussed in this paper is the influence of the soil properties at any given site on the behavior of the spacecraft during impact. In order to reduce the extremely large number of significant parameters to a number that can be reasonably dealt with, it will be assumed that the spacecraft will behave as a rigid body, that the striking surface of the spacecraft is spherical, and that the velocity vector at impact is perpendicular to the surface the surface of the soil. The assumption that is furthest from reality is that of the rigid body, since the striking surface will be a heat shield that will deform during impact. However, data obtained by working with a rigid body should be very useful in developing solutions to the impact behavior of the real spacecraft. In terms of physical properties, soils are complex materials, with engineering properties at a particular site varying widely with changes in environment. Two typical soils were selected for study, a cohesionless sand and a partially saturated, cohesive clay. A general discussion is presented of the load-deformation characteristics of these two soils, considering rate and magnitude of loading. A series of preliminary experiments is described in which accelerometer records were analyzed to obtain the behavior of various vehicles during impact. A tentative method is presented for predicting the behavior, under certain conditions, of a vehicle during impact.
Experimental Investigation of Large Helical Coil Springs for Ground-Shock Attenuation
Authors: Kirschner Francis , Baratoff Paul
Published: September 2005

Critical installations require that shock inputs of 50 G or higher be attenuated to less than 1 G. This can be accomplished by very soft helical coil springs, used in various arrangements relative to the center of gravity of the isolated units. The lack of experimental data on springs of extreme sizes—3-in. bar diameter—and their application for vertical and lateral shock protection was the reason for this investigation. Two specific applications are presented for helical coil springs: the first, an underground bottom spring-supported building in which the springs have to take simultaneous vertical and lateral deflection under combined vertical and lateral loads during full shock input; the second system, a pendulum suspension-type with four struts, each consisting of four springs in series, parallel arrangement. Design criteria for the springs, the measurement of their lateral and vertical load rates, and experimental stress analysis, with equipment developed for the purpose of testing large springs under high static and shock loads, are described and compared with the results of analytical investigations for stress distribution in the circular cross sections of helical compression springs under different loading conditions.
Intensity-Amplitude Functions of Wave Activity in the Superior-Olivary Complex of the Cat
Authors: Boudreau James C.
Published: September 2005

Wave activity in response to tonal stimuli was recorded in the superior-olivary complex of anesthetized cats. Increases in stimulus intensity yielded measurable increases in superior-olive potentials up to a limiting intensity. The intensity-amplitude curves were found to approximate power functions, with an average exponent of 0.34 for an 800-cps stimulus. The intensity-amplitude functions for stimuli between 200 and 2400 cps tended to form families of curves with maximum amplitudes between 500 and 1000 cps. The slopes of the functions tended to decrease with increasing stimulus frequency.
Neuronal Periodicities to Tones in Feline Auditory Medulla
Authors: Moushegian George , Whitcomb Milton A. , Rupert Allen
Published: September 2005

At the last meeting of this Society, evidence was presented for intrafiber volleying by units in the superior-olivary complex of cat. These results showed that an auditory unit could discharge during monaural tonal stimulation with interspike intervals that are equal to and multiples of the period of the stimulating tone up to about 2.0 kc/sec. Because these data were obtained with only a 20-channel data processor, long interspike intervals were unobtainable and were lost, therefore, in an overflow basket. By utilizing a computer (CAT) with 400 memory addresses, it has been possible in recent studies to retrieve most of the data with a resolution of 78 μsec. These preliminary findings show that interspike intervals that are many multiples of the period of the tone occur during stimulation. At 1.0 kc/sec, for instance, spikes occur at time intervals of 1, 2, 3, 4, …, to 30 msec and at 0.5 kc/sec the intervals are 2, 4, 6, 8, …, to 16 msec. The intervals, in both instances, are multiples of the period of the tone. The periodicity upon stimulation evidenced by these units, which are at least two synapses from the periphery, suggests that temporal analysis of information is maintained to at least this level of the auditory pathway.
Cytoarchitectural Changes in Corti's Organ after Kanamycin Treatment and Acoustic Trauma
Authors: Hawkins Joseph E. , Beger Valerie , Aran Jean-Marie
Published: September 2005

Changes in the cytoarchitectural pattern of the organ of Corti were studied in two groups of guinea pigs. One had been treated with kanamycin in doses of 200–400 mg/kg/day for 5–20 days. The other group had been exposed to tones of 500–4000 cps at 140–150 dB SPL. Examination of surface preparations of the organ of Corti by phase-contrast microscopy revealed loss of outer hair cells in both groups of animals. In the kanamycin group, the greatest loss was at the basal end of the organ of Corti. In the acoustic-trauma group, the site of loss varied somewhat, as might be expected, with the exposure frequency, but was greatest in the first and second turns. Severe destruction was visible under the dissecting microscope, without the aid of greater magnification. In acoustic trauma, loss of pillar cells was also seen, whereas kanamycin caused loss of Caludius cells in the basal turn. The results are illustrated with photomicrographs and maps of the organ of Corti.
Hearing and Feeling Sensations in Electric Fields
Authors: von Gierke Henning E. , Sommer H. C.
Published: September 2005

The hearing sensations stimulated by an audiofrequency current passed through various types of electrodes attached to different portions of the human head or body have been previously investigated and termed electrophonic hearing. More recently, modulated electromagnetic waves have been described to produce hearing sensations. The experiments reported in this paper investigated hearing phenomena in electrostatic fields when the whole head or parts of its surface are exposed to alternating electrostatic fields of audiofrequency. Threshold data obtained by this method are compared to the data reported by others for the different types of electrophonic stimulation mentioned above. Calculations show that all these types of auditory stimulation on the head surface of normal subjects can be explained quantitatively by mechanical tissue excitation by electrostatic forces. Application of this stimulation method for studying vibrotactile sensations on finger tips and other body areas, as well as research applications in psychoacoustics, are demonstrated and discussed.
Power Spectrum of Array Signal-Gain Fluctuations
Authors: Shapiro Arthur
Published: September 2005

It is known that the signal gain of an array of hydrophones fluctuates randomly in time. Several authors have investigated these fluctuations from different viewpoints; most of them determine meansquare array responses assuming correlated phase fluctuations. Since the signal gain varies with time, it should be regarded as a stochastic process. All attempts to find the multidimensional distribution functions of this process assuming Gaussian inputs have failed. It is not difficult, however, to develop an expression for the power spectrum of the gain fluctuations of the array output in terms of the spectra at the individual hydrophones and the cross spectra between the array elements. Data were taken on the individual elements of an array of five hydrophones and the spectrum of the array-gain variations was computed in accordance with the procedure to be presented. This spectrum is compared with the spectrum obtained directly from the fluctuations of the array output. It is hoped that measuring array fluctuations in terms of cross spectra between the individual hydrophones will give some insight into the mechanism causing the fluctuations. [Work supported by the U. S. Office of Naval Research.]
Measurement of Attenuation of 5- to 8-kc/sec Sound in Small Samples of Sea Water
Authors: Hansen Palle G.
Published: September 2005

Cavity resonators with acoustically soft side walls were developed for measuring sound attenuation in sea water. The equipment is capable of such measurements at discrete frequencies between 5 and 8 kc/sec, in the range from 10–200 dB/kyd. Natural sea water with suspended particulate matter and high oxygen content showed attenuation in the whole range in contrast to either distilled or clean sea water, which produced no measurable attenuation. It is suggested that fine bubbles or bubble nuclei may account for the excess attenuation. The above-mentioned conditions and results correlate well with earlier field measurements, where anomalous attenuations were observed.
Fluctuation Correlations in Randomly Inhomogeneous Media
Authors: Knollman G. C.
Published: September 2005

A theoretical presentation is made of the mutual correlation function for amplitude and phase fluctuations associated with acoustic-wave propagation in a statistically isotropic medium of small, random refractive variation. Both plane and spherical sound waves are considered. Large-scale inhomogeneities of arbitrary spheroidal shape (including the type involved in ocean acoustics) are treated, and the transmission range is regarded as large in comparison with the inhomogeneity scale in the transmitterto-receiver direction. The principal effects on amplitude-phase correlations of such factors as range, wave frequency and shape, and inhomogeneity shape are discussed, with particular emphasis placed on the low-and high-frequency limits of the analysis. [Work supported by the LMSC Independent Research Program.]
Propagation of Short-Wavelength Acoustic Waves through an Inhomogeneous Medium
Authors: Barnard G. R. , McCormack K.
Published: September 2005

Transmission coefficients calculated using a simple layered model that assumes average aeonstic properties for the inhomogeneous layer are compared to coefficients calculated using a more general solution for a variable index of refraction. Transmission-coefficient amplitudes and refraction angles are compared for several angles of incidence. The method of determining an expression for the velocity profile is discussed, along with the details of the transmission-coefficient calculation. [Work supported by the U. S. Navy Bureau of Ships.]
Extension of the Kirchoff-Helmholtz Equation
Authors: Hudimac A. A.
Published: September 2005

This paper considers the application of the Kirchhoff-Helmholtz equation to the determination of the acoustic field for an exterior problem for which the boundary condition is inhomogeneous Dirichlet. It is thus necessary to determine the normal derivative of the field function on the boundary. Horton has given a simple approximation for this in case the boundary is coincident with a wavefront and the radius of curvature is large as compared to a wavelength. Horton's approximation is extended to the case of a wavefront not coincident with the boundary by the use of the Huygen's principle. A more complete theory, ignoring only diffraction, is developed by an extension of the ray theory. It is further indicated how the latter theory can be applied to the determination of the crosspower spectrum of a noise field.
High-Q Quartz-Crystal System for Use in Absorption Measurements
Authors: Ghering Walter L.
Published: September 2005

A high-Q resonant system employing an x-cut quartz crystal was devised for use in absorption measurements of small samples. To determine the constants of the system, the Q of the system was measured under various clamping and loading conditions. The clamping losses were determined by comparing the system Q to the crystal Q in free fall in a vacuum. The system Q was found to be mainly a function of the clamping losses and various supporting methods were investigated. System Q's in the order of 800 000 were obtained, allowing the detection of the damping effect of a small sample or thin film. [Work supported by the U. S. Air Force, under contract AF-AFOSR-43-63.]
Recent Approaches to Echo-Structure Theory
Authors: Freedman A.
Published: September 2005

The results are described of an analysis of direct backscattering of acoustic waves by a rigid body. The body is assumed to be large in terms of wavelengths and immersed in an ideal, fluid medium. The echo is shown to be composed of a number of discrete pulses, each a replica of the transmission pulse, and hence termed an “image pulse.” An image pulse is generated whenever there is a discontinuity, with respect to range r, in dnW(r)/drn, where n=0, 1, 2, 3, ⋯, and W(r) is the solid angle subtended at the transducers by that part of the scattering body within range r. It is shown that four types of envelope of received signal arise from varying degrees of overlap of these image pulses. Experimental tests of acoustic backscattering using both complex and simple body shapes have given qualitative support to the theory. Some supporting quantitative evidence has been obtained. Certain discrepancies in magnitude have been ascribed to internal penetration effects.
Speech Recognition, Using Analog Threshold Logic
Authors: Martin T. B. , Zadell H. J. , Nelson A. L. , Herscher M. B.
Published: September 2005

A speech-analysis system using analog threshold logic (ATL) for feature abstraction is being developed to recognize consonants in utterances of CVC words by a number of talkers. The ATL element, originally modeled after the biological neuron, has an output that is linearly proportional to the net sum of excitatory and inhibitory inputs, provided that this net sum is greater than some adjustable threshold. The speech-analysis system abstracts relatively steady-state as well as transient features over almost 60 dB of dynamic range from the logarithmitized outputs of 19 low-Q filters. Feature abstraction takes place in real time, does not require segmentation, utilizes parallel processing, and provides information about both the presence and magnitude of the frequency-energy-temporal characteristics of speech sounds. Many features corresponding to results of speech-recognition experiments described in the literature have been automatically abstracted by ATL networks, which measure the slope of the spectral envelope in real time. Using the experimental system, recognition scores in the range of 82%–99% were obtained for 16 consonants. Results for the fricative consonants are discussed and some of their invariant features described. [Work supported by the U. S. Air Force Research and Technology Division, Air Force Avionics Laboratory.]
Frequency Modulation of Speech
Authors: Silbiger H. R.
Published: September 2005

Frequency modulation of speech is an effect produced by periodically modulating the speech frequencies during transmission. This effect is detectable by the wavering or buzzing quality that it imparts to the speech as received. The detection limits of frequency modulation of speech were determined using the Békésy tracking technique. Modulation rates from 10 to 200 cps were used on speech produced by both male and female talkers. Detection limits, expressed as a function of signal to sideband ratio, were found to vary as a function of sex of the talker, modulation rate, and received-speech level. Detectability is greater with female than with male talkers, and peaks at a higher modulation rate for the female talkers than for the male talkers.
Computer Evaluation of Pitch Extractors
Authors: Wade Fred B.
Published: September 2005

Development of pitch extractors is a continuous effort. Workers in this field need a quantitative, objective method for rapid evaluation and comparison of various techniques that are implemented. Previous methods involved laborious, visual comparison of the speech wave with the output of the pitch extractor or the use of unrealistic inputs such as a periodic pulse generator or a spoken list of isolated syllables. Recently, testing of pitch extractors was facilitated with the aid of a digital computer. A pitch-pulse master tape was produced from 6 min of clear speech, using techniques of B. Gold [J. Acoust. Soc. Am. 34, 916–921 (1962)]. A program was written to compare the “ideal” pitch pulses from the master tape with the outputs of experimental circuits having the same speech input. The program detects minor inaccuracies, as well as gross errors in pitch, and permits rapid diagnosis of circuit performance.
Pulse-Excited Vocoder System
Authors: Paulus E. , Rothauser E. H.
Published: September 2005

The set of subchannel signals of a vocoder can be transmitted by a time—or a frequency—multiplexing system. It is shown that pulse techniques allow for a considerable reduction of hardware of the desired goal for a vocoder system is not minimum transmission-channel capacity but minimum hardware. Instead of using a fixed time frame for the transmission signal and a fixed sampling rate, the simplified system samples and transmits spectral data at the instantaneous pitch frequency. Besides its application for speech transmission, the described system offers several advantages for speech processing with relatively small and slow computers. Experiences with a channel vocoder system connected to an IBM-1401 are reported.
Normalization of Spectral Information in a Pulse-Excited Channel-Vocoder System
Authors: Paulus E. , Rothauser E. H.
Published: September 2005

Speech synthesis in vocoder systems works under the assumption that the two constituents of the speech description in such systems are independent of each other. As this assumption is not completely true, the synthesized speech signals show distortions that can be avoided by proper preprocessing of the transmitted spectrum and pitch information before using it to control the synthetizer. The already known “spectrum-flattening” technique modifies the pitch-control signals. A new method is proposed that tries to secure “orthogonality” of the spectrum description and the pitch description by compensating pitch influence on the spectral description. It offers several advantages, especially in speech-processing installations where a channel vocoder is utilized in cooperation with a digital computer. The results of intelligibility measurements for speech synthetized from unprocessed spectrum data as well as from data processed by a computer are reported.
Decapitation and Recapitation, a Study of Voice Quality
Authors: Miller Joan E.
Published: September 2005

The familiar model of the speech spectrum as a product of the source spectrum times the vocal-tract transfer function suggests making an actual separation of the two for two different talkers followed by a recombining of the vocal tract of one talker with the source of the other. The calculations to effect such an interchange were made on a pitch-synchronous basis. Fourier coefficients were obtained for each period, the harmonic-amplitude spectrum was matched to obtain locations of the vocal tract poles, and these poles were divided from the spectrum. The pole data for an utterance by one talker could thus be recombined with the source spectral data for an utterance by another talker and the speech wave regenerated by Fourier synthesis. Source data for several talkers were tried, each with the same vocal tract and also a single source was applied to several “heads.” Listening tests were made of the resulting combinations in an attempt to determine the effect of glottal source versus vocal tract on speech quality and talker identification.
Pitch of Speech from a Talker Supplied with Various Amounts of Helium
Authors: Wathen-Dunn Weiant , Michaels Sheldon B. , Lieberman Philip
Published: September 2005

A talker is supplied with a breathing mixture from a modified anesthesiology apparatus. The gas contains 20% oxygen, but the remainder consists of nitrogen and helium, the proportions of which may be varied to give several test conditions. In each case, the subject breathes the gas for a sufficient time before talking so that exhalation equilibrium is established. The talker then removes the breathing apparatus, produces a short utterance in a single exhalation, replaces the apparatus, and reestablishes equilibrium, repeating this as many times as may be necessary for the test. The exhaled gas is fed to a tube in which the velocity of sound is continuously monitored by measuring the time that it takes a pulse to travel the known length of the tube. In order to investigate possible acoustical-feedback effects, the subject's hearing is masked by noise for some of the runs. Data on fundamental voicing periodicities in the several cases are presented.
Vibrations Excited by Statistically Fluctuating Forces
Authors: Skudrzyk E. J.
Published: September 2005

The response of a mechanical vibrator to statistical forces can be computed by Fourier methods on the basis of the natural-mode solution or with the aid of the pulse response of the system. The second method leads to a convolution type integral of the time functions as they correspond to the factors in the integrand of the Fourier integral obtained by the first method. If the spectrum is similar to that of flow noise in the boundary layer of a moving vehicle, the solution for the amplitude is found to consist of two terms, one representing the forced vibrations of the modes because of the low-frequency part of the force spectrum, the second representing the contributions of the natural modes that are excited by the force spectrum in their resonance range. The first part of the solution, since it is a first vibration outside the resonance range of the modes, is independent of the damping; the second, being made up of the contributions of the resonant ranges of the natural modes, depends on the damping. Because of the existence of these two terms, the modal velocity may be very different from the product of the modal amplitude and the resonant frequency of the mode. In contrast to the modal amplitude, the modal velocity is predominantly determined by the contributions of the modes in their resonance range, and the solution for the modal velocity is a relatively simple function of the damping of the system.
Simulating Missile-Firing Acoustical Environment by Means of Equivalent Vibration
Authors: Putukian John H.
Published: September 2005

This paper describes the experimental effort undertaken to simulate the acoustical environment of the electronic packages of the target search and firing-control radar systems of a mobile missile system during a missile firing. The basic idea is the use of high-frequency shakers to replace the prohibitive cost of laboratory testing to high-power broad-band acoustic fields. The missile-firing environment of a typical package is given as composed of the spectra of (a) the reverberant acoustic field around the package and (b) the random mechanical-vibration input at the mounting points. By the use of a reverberant acoustic chamber, the vibratory response of the sensitive electronic component is monitored and the response extrapolated to the high-intensity acoustic levels. The feasibility of simulating the missile-firing environment is discussed. It is shown, by a theoretical approach, that a “modified” steady-state test is suitable even for a transient environment. Operating tests of electronic units in the simulated acoustic environment as high as 171 dB over-all SPL are described. Some design techniques employed to permit satisfactory performance of sensitive electronic units in the high-level acoustic environment are briefly discussed.
Model Experiments on Flooded and Air-Backed Cylindrical Radiators
Authors: Chieu N. T. , Middleton F. H.
Published: September 2005

Scale modeling of deep-submergence cylindrical radiators is helpful in design work. It is easy to make configuration changes in a ring, one at a time, to observe the effect on radiation pattern, driving-point impedance, and on conversion efficiency. The model ceramic rings employed in this study were either 1 or 112 in. o.d. with heights ranging from 14 to 112 in. Ring pairs were made identical in every respect except height. Thus, the effect of changes in the height-to-diameter ratio were isolated. The model rings were all operated at frequencies of the fundamental breathing mode and well above, both flooded and air-backed. The results include radiation patterns, impedance curves, and measured efficiency for each ring in both the flooded and air-backed arrangement. Some of the multilobe patterns associated with the higher-order modes are discussed in comparison with those predicted by a mathematical model of the radiator, programmed on a digital computer. The computer program was presented at the last meeting of the ASA. [Work supported by the U. S. Office of Naval Research, Acoustics Programs.]
Free Circular Disk with Constant Pressure Distribution
Authors: Arase Elizabeth M.
Published: September 2005

A thin rigid vibrating circular disk with constant-pressure distribution on its surface in an infinite soft baffle corresponds mathematically to the solution of the wave equation with homogeneous Dirichlet boundary conditions. Its characteristics may thus be determined by the evaluation of integrals. The velocity distribution on the disk has been found for various sizes and is compared with those for a disk in an infinite rigid baffle [V. Mangulis, Tech. Rept. TRG-142-TN-64-2 (1964)]. The impedance and radiation pattern is given for various disks (ka<2) and compared with the corresponding quantities for the soft- and rigid-baffle constant-velocity disk as well as with the rigid-baffle constant-pressure disk. The radiation characteristics for the same type of baffle are similar and may be estimated for the constant-velocity disk from the constant-pressure disk for other shapes of radiators. [Hudson Labs. Columbia Univ. Informal Doc. No. 54.] [Work supported by the U. S. Office of Naval Research.]
Low-Frequency Attenuation of Rigid-Frame Ear Defenders
Authors: Thiessen George J.
Published: September 2005

In the region of 100 cps, the attenuation, as measured by the treshhold shift, of an ear defender with a rigid frame supporting the cups with liquid-filled cushions is very nearly the same as when the cups are supported by a flexible frame. However, when using an artificial head, the attenuation is appreciably different for the two frames, even though sponge rubber is used to simulate the flesh. If only the spring constant of the system were important, the difference in attenuation for the two frames should be about 20 dB. The actual difference for the artificial head was about 8–15 dB. It is postulated that the lack of rigidity of the human skin may be the relevant factor, since this would allow a certain amount of flow in response to the sound pressure.
Some Properties of the Acoustic Reflex in Man
Authors: Lilly David J.
Published: September 2005

This paper describes instrumentation and a technique for measurement of both static acoustic impedance and changes in complex acoustic impedance at the tympanic membrane. White noise was used to activate the acoustic reflex. Five subjects were exposed to this noise at levels between 50 and 110 dB SPL (over all) and with durations between 5 msec and 10 min. Changes in acoustic impedance were recorded at the subject's right ear while the noise was presented to his left. At some noise levels, the acoustic reflex was sustained for at least 10 min. The latency and strength of the reflex, and its adaptation, all were related to the level of the noise. Time required for a maximum change in acoustic impedance was related inversely to noise level. Pulsed noise was more effective than steady noise in eliciting the reflex. The acoustic reflex was observed, on the average, at an over-all SPL of 69 dB for steady noise and 63 dB for pulsed noise. [Work supported by program, project grant B-3856 from the National Institute of Neurological Diseases and Blindness, National Institutes of Health. U. S. Department of Health, Education, and Welfare.]
Evoked Vocal Response of the Bullfrog
Authors: Capranica Robert R.
Published: September 2005

A quantitative study of a highly selective behavioral response to sound in the bullfrog is described. The males of a laboratory colony respond vocally to a restricted class of natural and synthetic sounds. A necessary condition to elicit calling is the simultaneous presence of sufficient sound energy in the frequency regions of 100–400 and 1000–2000 cps. The relative amplitudes of the spectral envelopes of these two regions can independently vary over a wide range (at least 50 dB) without noticeably affecting calling performance. Calling can be suppressed by the introduction of energy in the neighborhood of 500 cps. The degree of suppression depends on the relative spectral amplitudes of the introduced energy and the energy in the lower frequency range of 100–400 cps. A comparison of temporal fine structure indicates optimum calling to waveform periodicities of approximately 100 cps. In presentations of the mating calls of 34 different species, only the call of the bullfrog evokes the vocal response. [Work supported in part by the U. S. Army, U. S. Navy, and U. S. Air Force under contract DA-36-039-AMC-03200(E); National Institutes of Health, U. S. Department of Health, Education, and Welfare (grant MH-04737-04); National Science Foundation (grant GP-2495); and National Aeronautics and Space Administration (grant NsG-496).]