bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of reverberation time in the National Bureau of Standards reverberation room
Authors: Bartel Thomas W. , Magrab Edward B.
Published: October 2005

The spatial variation of the reverberation time in the 1/3-octave bands from 80 to 10 000 Hz was studied as a function of: (1) the surface area of the absorbing material ranging from 0 to 13.4 m2; (2) the orientation and rotational speed (0–10 rpm) of the vanes; (3) loudspeaker placement and type; (4) discrete microphone versus high-speed multiplexed data acquisition; (5) the number of microphones; and (6) the number of decay times averaged at a given microphone location. For the case of the vanes rotating at 7.5 rpm it was found that the standard deviation of spatial variation of the reverberation time from 12 microphones ranged from 1% to 12% of the mean value in the frequency bands below 400 Hz, was less than 0.5% from 400 to 5000 Hz and increased to 1.5% at 10 000 Hz. The values were virtually independent of the surface area of the absorbing material placed in the room. With the vanes stationary these percentages increased by as much as a factor of 5. In addition to the decrease in the spatial variance with the vanes rotating, the spatially-averaged reverberation time decreased by 2% to 15% in the frequency bands below 500 Hz.
Equivalence of eigenmode and free-wave models of steady-state reverberation in rectangular rooms
Authors: Lubman David
Published: October 2005

The eigenmode and free-wave models of steady-state reverberant sound field in rooms are sometimes mistakenly believed to be unrelated representations. These two models are shown to coincide for the case of rectangular rooms, for which the axial, tangential, and oblique modes can be decomposed into two, four and eight travelling plane waves, respectively. (This was pointed out by Morse and Bolt [Rev. Mod. Phys. 16 (2), 85 (1944)].) Above the frequency of modal overlap, therefore, the reverberant sound field in a rectangular room may be viewed as an ensemble of many plane waves arriving from many directions in space. This provides justification for use of the free-wave model.
Representation of target range in the sonar receivers of echolocating bats
Authors: Simmons James A. , Lavender W. A.
Published: October 2005

Echolocating bats can discriminate the range (echo arrival time) of simulated targets with accuracy predictable directly from the sonar waveforms down to the region where echo and noise powers are about equal. Detection and ranging performance are closely linked. Equivalence of performance in simultaneous- and successive-presentation procedures indicates that bats make absolute range judgments and store range images of targets for subsequent comparisons. Targets separated in range and/or angular direction are perceived as distinct events. Although target range is perceived noncoherently, target fine structure may be perceived coherently. Information about the occurrence and timing of transmitted sounds and echoes is conveyed in the time domain over frequency-specific primary auditory neurons and appears, still in the time domain, ascending the lateral lemniscus and in the inferior colliculus. Behavioral data suggest ultimate spatial “receptor-field” representation of range in the brain, so echo-timing information may be receded into range-specific neurons at or above the inferior colliculus. The data generally suggest that target range is processed by channels used for periodicity-pitch perception in nonecholocating animals. [Work supported by NSF.]
Range resolution by an echolocating bottlenosed dolphin (Tursiops truncatus)
Authors: Murchison A. Earl
Published: October 2005

Utilizing a two alternative, forced-choice (simultaneous stimuli presentation) procedure, the ability of a bottlenosed dolphin (Tursiops truncatus) to discriminate differences in target range by echolocation was determined. Target-range difference discrimination trials were conducted at three different absolute ranges (1, 3, and 7 m). The range resolution acuity of the dolphin varied with absolute range. His 0.79 hit rate probability for the absolute range of one m was 0.9-cm range difference; for the absolute range of 3 m it was 1.5 cm and for an absolute range of 7 m it was 2.8 cm. Behavioral data suggest that these levels of perceptual acuity are not usually attained and/or maintained during the dolphin's normal nonstatic prey pursuit. [Work supported by NUC.]
Echolocation discrimination of complex planar targets by the Beluga whale (Delphinapterus leucas)
Authors: Gurevich V. S. , Evans W. E.
Published: October 2005

Results of a study of a Beluga trained to discriminate between two complex planar targets, indicate that this animal's echolocation discrimination capability with and without blindfolds is superior to that of bottlenosed dolphins tested on similar targets. The standard target used was a three-step pyramid constructed of three polyvinyl chloride sheets each 13 mm thick. The first step was 10×10 cm, the second step was 7×7 cm and the third step was 3×3 cm. The selection of the standard target was considered a correct response. The comparison targets (incorrect choice) differed from the standard target only in the size (surface area) of the third step. With a comparison of a third step of 2.9×2.9 cm versus the standard, 3.0×3. 0 cm, the animal's mean correct response was 80.8% correct. When presented with two standard or identical targets the mean response dropped to chance (55. 5%). The performance of the bottlenosed dolphins tested on similar targets dropped to chance on a comparison of 2.7×2.7 cm versus 3.0×3.0 cm. The pulses used by the Beluga during the echolocation discrimination task contain very little acoustic energy below 12 kHz with the peak energy occurring at 40, 80, and 120 kHz. The measurements of the frequency components in the echolocation signal above 110 kHz are only tentatively believed due to limitations in the frequency response characteristics of the hydrophones used. The ability to use both sensory channels (tests without blindfolds) appeared to enhance discrimination ability slightly. [Work supported by NUC.]
Electro-optic hydrophone
Authors: Hanish S. , Chovan J.
Published: October 2005

The electro-optic hydrophone is a device that detects sound in water by scattering a laser beam off naturally occurring particles moving under the influence of acoustic signals. The theory of operation is the same as that of cw Doppler radar or (alternatively) of an optical heterodyne in which the laser beam is split into two beams to form a set of real (or virtual) fringes at the focal volume in the water [Rudd, J. Sci. Inst. 2, 55 (1969)]. Moving particles traverse these fringes and are intermittently illuminated. A photodetector converts the scattered light intensity into an intermittent electric current which is processed in a power spectrum analyzer. A laboratory experiment is described in which an acoustic signal at 200 Hz and peak amplitude of 4.35×10 (−8) m is detected by this principle. A discussion is then made of the minimum detectable signal of this device in the presence of noise from various origins. Methods are proposed to lower the threshold of detection from the level currently achieved.
Optimally wide-band lightweight flextensional transducer
Authors: Brigham G.
Published: October 2005

An experimental Class IV Flextensional transducer consisting of three identical air-backed modules, built and tested in 1969 at the Autonetics Division of Rockwell International, generated a 40 dB/V (re 1 μbar at 1 yd) source level over a 3-dB bandwidth of 1.7–6.5 kHz. From a detailed analysis of this type of transducer it appears the use of glass reinforced plastic oval shells to replace the aluminum shells, stagger tuned modules, and compliant coupling of ceramic bar to shell would result in an experimental transducer of lighter weight and much larger bandwidth than the previous unit. The acoustic effects of an oil filling used for pressure compensation to depths in excess of five hundred feet but less than about 2000 ft in the ocean can be at least partially offset by use of HY300 steel psuedocompliant tubes molded into the inner walls of the GRP shells. This paper presents the performance characteristics, weight, and geometry of the older unit and discusses the basic design features of this type of transducer.
Shipboard shock environment and its measurement
Authors: Oleson M. W. , Belsheim R. O.
Published: October 2005

The design and acceptance of machinery and equipment for shipboard use requires knowledge of the shock environment produced by noncontact underwater explosions. Structural and response considerations preclude accurate prediction of this environment without experimental confirmation. The Navy has conducted many experiments to measure shipboard shock environment and its effect on internal items. This data and results from dynamic analyses yield a general understanding of the shipboard shock environment, but this understanding is restricted to ships resembling those for which experimental data exists. This paper discusses the varied types of shock environment which may be expected on small and large ships. An important factor for response studies is the dynamic interaction between a machine and the ship structure. The kinds of shock measurements and the means of interpreting these data are outlined and the results of several underwater-explosion test series against operating ships are summarized. These data are discussed in terms of the types of shock environment and the interpretive analyses of the shock measurements. A concluding section reviews capabilities for predicting shock environment of present and variant ship designs.
Dynamic considerations in the design of floating nuclear power plants (FNPP)
Authors: Amir G. G. , Kapur K. K.
Published: October 2005

Design criteria and their implementation in the FNPP when subjected to dynamic effects are discussed. The FNPP idea was proposed in the late 1960's because of site flexibility, immediate abundance of water, possible decoupling from seismic shock, and because the concept lends itself to a high level of standardization. The FNPP, when located offshore, must be protected by a breakwater to which it is permanently fastened by a mooring system. The dynamic considerations affecting the design of the FNPP are due to natural phenomena, accidents, and man-made adverse conditions. Tornadoes, hurricanes, tsunami waves, and ice loading are considered for both safe operation and safe shutdown of the plant. Earthquakes, sub-marine slides, and underwater currents are considered for the breakwater design as well as for their effect on the FNPP through the mooring system. The above conditions are investigated by model test and analysis of the seabed-fluid-structure interaction. Accident conditions such as ship collisions with the breakwater, shipping accidents resulting in air blast, and aircraft crash are examined by statistical and probability methods and by structural testing and analysis.
Lip larynx interaction models for intervocalic /p/ production
Authors: Putnam Anne H. B. , Doherty E. Thomas , Shipp Thomas
Published: October 2005

Simultaneous recordings of labial and laryngeal EMG, subglottal and intraoral pressures, and voice were obtained from six talkers to study lip/larynx interaction during production of intervocalic /p/ in three talking conditions: subjects spoke normally, with the jaw fixed, and with a transoral pressure-release device. Schematic models were used to categorize the temporal and magnitude details of the sequence of articulatory events for /p/ in each condition. Multivariate regression analyses isolated those differences between control and experimental conditions which implied a significant change in motor programming for /p/ when normal lip/larynx articulation was modified experimentally. Treatment of the data thus far reveals that when the jaw is fixed, significant readjustment for production of /p/ occurs only in lip-muscle activity patterns. For the pressure-release-device condition, aerodynamic, and voicing patterns for /p/ are altered when intraoral pressure is unexpectedly released, but preliminary statistical analysis reveals no significant concomitant readjustment in laryngeal-muscle activity. [Work supported by NIH and VA Research Service.]
EMG study of the coarticulation of lip rounding
Authors: Bell-Berti F. , Harris K. S.
Published: October 2005

The extent of both anticipatory and carryover coarticulation is of central importance to theories of speech organization. One articulatory gesture whose anticipation has been studied repeatedly is vowel lip rounding. Daniloff and Moll [J. Speech Hear. Res. 11, 707–721 (1968)], reporting the results of a cinéfluorographic study of lip rounding, describe vowel lip rounding as being initiated with the beginning of a preceding consonant string, for strings up to four segments long. Preliminary results of an EMG experiment in which /u/ was preceded by a one- or two-consonant string show activity for the rounding gesture beginning at the same time before the vowel onset for all conditions regardless of the position of the syllable boundary. Parallel results were obtained for carryover coarticulation.
Laryngeal timing constraints in plosive-vowel and fricative-vowel syllables, or: Is VOT really the best measure of glottal-supraglottal timing?
Authors: Klee T. M. , Weismer G. , Ingrisano D. R.
Published: October 2005

Voice-onset time (VOT) is generally defined as the time interval between release of an occlusive consonant and the onset of vocal-cord vibration. This description, however, does not allow a simple comparison of glottal-supraglottal timing between syllables initiated with stop and fricative manners of articulation, since the time of release associated with fricative is less well defined than that associated with stops. We compare glottal-supraglottal timing across consonant manner of articulation by normalizing the duration of selected target utterances spoken in a sentence frame by 15 subjects, and deriving a measure which expresses the timing of glottal-supraglottal events relative to the duration of a potential unit of articulatory encoding, viz., the syllable. Additional motivation for developing an alternative measure to VOT comes from preliminary data reported by Umeda and Coker [J. Phonetics 2, 1–5 (1974)], which suggests that stop closure duration and VOT are not independent in connected speech. We discuss our results relative to the aerodynamics of consonant production, and the potential limitations of the VOT measure as currently defined.
Magnitude of perioral reflexes as a function of stimulus velocity and isometric lip force
Authors: Larson Charles R. , Folkins John W. , McClean Mike , Muller Eric M.
Published: October 2005

A quantitative description of peripheral nervous-system function may enhance our ability to analyze speech motor control. With respect to lip motor control, recent evidence [R. Netsell and J. Abbs, J. Acoust. Soc. Am. 58, S41 (1975)] suggests that perioral reflexes may be actively modulated throughout lip movement for speech. In the present study, factors explored to clarify the manner in which these reflexes may be modulated during control of lip movement. Previous studies of perioral reflexes have been handicapped by the inability to systematically vary the characteristics of the mechanical simulus. The present investigation utilized an electromagnet under displacement sensitive servo control, coupled to a force transduction system, which delivered mechanical stimuli of different velocities against the lip of normal adult subjects. Reflexes were recorded from hooked-wire EMG electrodes inserted into the orbicularis oris muscle while the lip was either passive or exerting an isometric force. Perioral reflexes were found to increase in magnitude as a function of both stimulus velocity and the level of isometric force. [Work supported by NIH.]
Syllable-final nasal elements in English—an x-ray study of velum height
Authors: Fujimura O. , Miller J. E. , Kiritani S.
Published: October 2005

An English syllable can contain, in the final part, a nasal consonant either as the main consonant with place specification as in “den,” “denned,” etc., or with another true consonant within the syllable core, as in “dent,” etc. [O. Fujimura, J. Acoust. Soc. Am. 59, Z5 (A) (1976)]. A set of English monosyllabic words containing various syllable-final clusters were uttered by a native speaker of American English, and the movements of the velum as well as three selected points on the tongue, a lower tooth, and the lower lip were tracked by means of the computer-controlled x-ray microbeam system [S. Kiritani, K. Itoh, and O. Fujimura, J. Acoust. Soc. Am. 57, 1516–1520 (1975)]. The data contained about 300 such word utterances as well as several sentences, and have been examined with particular reference to the above-mentioned distinction in terms of exact articulatory characteristics. The results will be discussed also in comparison with previous findings about Japanese nasal consonants in different intrasyllabic positions [O. Fujimura, J.E. Miller, and S. Kiritani, J. Acoust. Soc. Am. 58, V5 (A) (1975)].
The function of strap muscles in speech: pitch lowering or jaw opening
Authors: Atkinson James E. , Erickson Donna
Published: October 2005

This paper reports on one aspect of a continuing study to determine the physiological correlates of the changes in fundamental voice frequency (F0). Several electromyographic (EMG) studies with speech have reported an association of strap-muscle activity, particularly the sternohyoid, with low F0 and some of these studies suggest that the sternohyoid is actively involved in lowering F0. It has also been suggested, however, that the sternohoid is involved with jaw opening, and that the reported pitch-lowering effects may actually be the result of jaw opening. To investigate this question an EMG experiment was conducted on one speaker of American English under normal and clenched jaw conditions. The normal utterances were of the form “Bev loves Bob” with emphasis on the various words. The clenched-jaw data were obtained while the subject held his jaw fixed by biting on a tongue depressor and intoned the corresponding intonation patterns with a fixed vowel carrier /a/. The results indicate that the strap muscle activity for the normal utterances is very similar to the activity for the same intonation pattern with the jaw clenched. Strap-muscle activity thus seems to be more closely related to pitch effects than to jaw-opening effects.
Effects of subglottal pressure changes on sustained phonation
Authors: Baer Thomas
Published: October 2005

The intrinsic dependence of fundamental frequency of phonation on subglottal pressure has been studied in several investigations by producing involuntary changes in pressure. In some of these experiments, the pressure changes were produced by suddenly pressing at random intervals on the chest of a phonating subject. Muscle activity was assumed constant in the first few pitch periods immediately following the beginning of pressure rise. In the present investigation, the chest-pushing paradigm was used while both subglottal pressure and the electromyographic activity of several laryngeal muscles were recorded. In a preliminary experiment, fundamental frequency was found to vary with subglottal pressure at average rates of 3–5 Hz/cm H2O. However, electromyographic responses of some intrinsic laryngeal muscles were found to begin very shortly after the beginning of the pressure rise. Average delays for the vocalis muscle for three conditions ranged from 0 to 30 msec. Variations in vocal intensity more closely paralleled the changes in pressure than did fundamental frequency. Implications of these results will be discussed.
Persistence of learned motor patterns in speech
Authors: Hamlet S. , Stone M. , McCarthy T.
Published: October 2005

It has been noted that “spontaneous” compensations are made during speech for articulatory constraints such as clenching of the jaw. On the other hand, at least several days are required for speech adaptation to a dental prosthesis. A recording of speech and physiological data on jaw activity and tongue contacts was made at the time of initial insertion of an experimental dental prosthesis. Subjects wore the prothesis for two weeks of adaptation, after which a second recording was made, and then waited at least 1 month without experience in speaking with it. A follow-up recording was then made with the same protocol as when the prosthesis was first inserted. Speech sounded much less disturbed by the insertion of the prothesis after a lapse of a month than it had at initial insertion—knowledge of the compensatory adjustments required had evidently been retained over that period of time. Palatographic data showed a rapid progression toward the compensatory pattern within a few repetitions of the speech sample. [Work supported by NIH.]
Voluntary reaction times for phonation initiation
Authors: Izdebski Krzysztof , Shipp Thomas
Published: October 2005

Simple neuromechanical reaction times for voluntary initiation of phonation were investigated in 15 males and 15 females as a function of (1) stimulus type: either a 1-kHz tone or a drop from 6 cm H2O in intraoral air pressure to atmospheric pressure; (2) abducted, adducted, or uncontrolled prephonatory vocal-fold position and (3) 75%, 50%, and 25%, of subject's lung volume. Auditory-manual responses were also obtained from these same subjects. All responses were to stimulus onset. The fastest neuromechanical reaction times were 120 msec; however, the average time for phonation initiation across subjects was 180 msec. Auditory-vocal reaction times were generally faster than somesthetic-vocal reaction times, but these differences were not significant. Faster auditory-vocal reaction times were obtained at mid than at lung volume extremes, as well as when phonation was initiated from abducted rather than adducted prephonatory vocal-fold positions. Manual reaction times were significantly faster than vocal reaction times.
Comparison of Doppler sodar antenna configurations used for horizontal wind measurement
Authors: Davey Robert F.
Published: October 2005

The performance of two antenna configurations is evaluated using a parametric optimization technique which predicts the relative accuracy of horizontal wind measurement. Consideration is given to the effect of atmospheric attenuation and the relation between the thermal and velocity structure functions as well as to the geometric effects. Using a baseline case with a maximum measuring altitude of 500 m, optimum antenna orientations are determined for the familiar axisymmetric three-transmitter configuration and for a two-transmitter system using a tilted receiver antenna. The sensitivity of each system to small changes in the geometry and to modifications in the assumed attenuation and structure function ratio is examined. The two-transmitter system is found to generate velocity measurements with accuracy comparable to the three-transmitter geometry at the design point. However, the effect of the preferred orientation at lower heights results in poorer comparative performance.
High-powered acoustic transmitter for atmospheric sounders
Authors: Priestley J. Tant
Published: October 2005

A high-power narrow-beam acoustic transmitter for use in an atmospheric sounder has been designed and evaluated. The transmitter uses thirteen electroacoustic horn drivers manifolded to a 2-m aperture horn-reflector antenna. The evaluation of the transmitter included measurements of beam pattern, total efficiency, efficiency of individual drivers, total power output, and finite amplitude distortion. In particular at a frequency of 1250 Hz the 3-dB beamwidth was 9°, the total efficiency was 10%, individual driver efficiency was approximately 17%, and the total power output was approximately 50 acoustic watts. At this power power finite amplitude distortion was quite perceptible at the mouth of the horn.
Three recent advances in acoustic sounding instrumentation and data handling at SRI
Authors: Uthe E. E. , Russell P. B. , Nielsen N. B.
Published: October 2005

Three recent technology developments at SRI are being used to improve the quality of acoustic sounder measurements and to facilitate the storage and interpretation of acoustic data. These are (1) Dual digitization and television display of simultaneous acoustic sounder and lidar data using a minicomputer-based system [E. E. Uthe and R.J. Allen, Opt. Quant. Electron. 7, 121–129 (1975)]; (2) Substitution of a larger dish and enclosure for the standard Aerovironment model; and (3) Microfilm storage of acoustic records, with machine-assisted transfer of layer heights and transition times to computer cards or tape. Examples demonstrating the utility of each technique will be shown.
Use of a nearfield array for acoustic backscattering cross-section measurements
Authors: Fiorito Ralph , Madigosky Walter
Published: October 2005

It is theoretically demonstrated that a large circular piston in an infinite rigid baffle operating at high frequency can be used as a nearfield array (NFA) to measure farfield backscattering (sonar) cross sections. Pulsed experiments are described which use the same piston both to insonify the object and receive the scattered wave. In transmitting, the piston produces a collimated plane wave within its Rayleigh zone. When the scatterer is placed within this zone, the scattered wave is received by the piston and integrated to reproduce a voltage response proportional to the scatterer's farfield amplitude function (NFA reciprocity principle). Measurements have been made on spheres and cylinders as well as model ships, insonified by a 4.75-in. circular beam at a frequency of 15 MHz. The sonar cross sections (target strengths) obtained are in good agreement with those theoretically predicted by finite beam insonification scattering theory. Comparison of scaled model ship measurements with full-scale target strength values shows reasonable agreement as well. [Work supported by NAVSEA-034.]
Effects of stimulus duration upon the response characteristics of single neurons in the inferior colliculus of unanesthetized bats (Tadarida brasiliensis mexicana)
Authors: Marsh D. S. , Pollak G. D. , Bodenhamer R. D.
Published: October 2005

Constant frequency (CF) and frequency-modulated (FM) pulses were utilized to examine the response characteristics of collicular neurons. Tonic, toniclike and various types of phasic “on” responses were noted depending upon the type of stimulus used. For example, a tonic response patten elicited from a given neuron with CF stimulation could be changed to a phasic “on” pattern with FM stimulation. Similarly, thresholds and input—output functions were affected by the stimulus type. Superimposed upon the effects of stimulus type were the effects of stimulus duration. Many neurons were found to have firing patterns and response characteristics to long duration stimuli that differed greatly from those observed with shorter signals having durations less than 2.0 msec. Results suggest that most inferior collicular neurons are best suited for extracting information from signals having durations comparable to those emitted during the search and approach phases of goal-directed flight and are poorly suited for responding to shorter signals having durations typical of those emitted during the terminal phase of echolocation. [Supported by NSF Grant P401855-000.]
Signal duration and its effect on recovery characteristics of single units in the inferior colliculus of unanesthetized bats
Authors: Bodenhamer R. , Pollak G. D. , Marsh D. S.
Published: October 2005

Recovery cycles were obtained from single units in the inferior colliculus of awake Mexican free-tailed bats (Tadarida brasiliensis mexicana) by recording responses to simulated pulse-echo pairs. The pulse-echo pairs were designed to mimic natural outgoing cries and returning echoes, and were either constant frequency tones or as in most instances, frequency-modulated tones. Since echolocating bats systematically vary pulse duration as they progress towards a target, we asked what effects these duration changes might have on neuronal recovery. Therefore, the durations of the simulated pulse and echo were varied from 1–10 msec and recovery observed with several signal durations. Even at short interpulse intervals and with initial pulses 25–50 dB more intense than the following “echoes,” the majority of units recovered well when signal durations were 3.4 msec or longer. Recovery with signal durations of less than 2, 0 msec, however, was typically poor. The results indicate that individual units may show strikingly different recovery patterns when durations of the stimulating pulse and echo are changed. This suggests that some units of the colliculus may only be encoding incoming information during restricted segments of the echolocation cycle, or alternatively, that single units may be involved in encoding different types of information during different segments of the echolocation cycle. [Supported by NSF Grant P401855-000.]
Survey of nonexplosive sources for acoustic propagation measurements
Authors: Cawley J. H.
Published: October 2005

Since the mid 1940's explosive charges have been widely used by offshore seismic exploration companies, by the U. S. Navy, and by other groups to generate high-intensity acoustic pulses for seismic and sonar-related activities. In the late 1950's offshore exploration groups began to develop alternate energy sources, and in the mid 1960's a number of non-explosive impulse and cw marine sound sources were introduced and soon dominated the offshore exploration field. Despite their relatively low-energy levels, these sources have since been tailored to reproducibly generate acoustic spectra concentrated in the range below 100 Hz at efficiency levels that have allowed them to completely replace shallow-detonated explosives. This report briefly describes important characteristics of four classes of nonexplosive acoustic impulse sources developed for offshore seismic exploration purposes and compares their acoustic signatures with those of explosive SUS charges used in sonar propagation studies. The total energy levels of SUS and several nonexplosive impulse sources are compared and acoustic levels, bubble pulse, and the spectral characteristics of the signatures are discussed and methods for defining and controlling these characteristics are briefly described. [Work supported by ONR/LRAPP.]
Hydroacoustic impulse sound source
Authors: Bouyoucos J. V.
Published: October 2005

An impulse source concept is described in which the potential energy of the pressure head of an underwater environment is converted to kinetic energy of an imploding flow which, in turn, is converted to an acoustic impulse free of after-shot clutter. This energy conversion concept has been realized in various hardware forms under the designation HYDROSHOCK.® It is characteristic of this class of source that considerable latitude exists in specifying the spectral level and spectral shape of the transmitted signal. The conversion mechanisms will be outlined, and the properties of several of the existing HYDROSHOCK® devices will be described. One recently developed source exhibits a peak source level of 255 dB re 1 μPa at 1 m, a pulse duration of 40 μsec, and a useful spectrum extending from 20 Hz to 100 kHz. The trade offs in source configuration between source level and bandwidth will be described, and comparisons will be made to spark sources, air guns, and various explosive devices. Applications for such impulse sources will also be reviewed. [This research has been supported by the Office of Naval Research, Code 222.]
Underwater explosion sources
Authors: Christian Ermine A.
Published: October 2005

Explosions have been used as underwater acoustic sources for many years, sometimes at rates exceeding 50 000 charges a year. During the past decade the types of studies undertaken with explosion sources have changed in character, and the requirements on charge levels have become more demanding. For example, an accuracy of ±1 dB in narrow-band levels is now desired for propagation-loss measurements in the 25 to 300 Hz frequency range. Fixed explosion source levels of such accuracy can only be accomplished if the charge depth is closely controlled; but strict depth control severely limits the type of experiment that is feasible. Compromise techniques for effective utilization of explosion sources are being developed. Recent progress along two avenues of attack on the problem—improved methods of describing the explosion sound field, and of taking the source characteristics into account during farfield data analysis—will be reviewed.
Use of the complex dynamic shear stiffness of a visco-elastic liquid to illustrate the origins of structural damping
Authors: Ely R. A.
Published: October 2005

The same complex stiffness notation which causes damping of solids and structures to appear to be independent of frequency and dependent on amplitude is shown to have descriptions of frequency-dependent, velocity-dependent, viscous damping hidden within it. That revelation is consistent with recent papers which report that only a viscous component of structural damping need be measured or modelled mathematically. Those papers also report that viscous damping accounts for all of the energy loss from built-up structures (as elementary dimensional analysis shows it must), This paper draws upon measured values of the dissipative and elastic components of the complex dynamic viscosity and stiffness of a viscoelastic liquid to illustrate conceptual continuity from damping in liquids to damping in solids.
Errors in power spectral density estimates of vibration test data
Authors: Austin M. E.
Published: October 2005

Estimates of power spectral densities obtained using time-compression, swept-filter spectral analyzers may contain errors due to assumptions regarding normality, randomness and symmetry of the data being processed. This paper considers possible errors in these estimates caused by various effects. The first concern is for hidden periodic components in data records assumed to be entirely random. Expressions describing this error are developed. Also of concern are nonlinear effects in the instrumentation which may result in amplitude-limiting of data records. Error analysis is performed for several possible amplitude distributions. Finally errors due to asymmetrical data records are considered. Records which are not normally-distributed in amplitude exhibit some degree of asymmetry and thus the power spectral density estimates obtained from these records will be in error. Expressions for power spectral density estimates of amplitude distributions other than normal are developed. These are compared with estimates obtained under the normal assumption. Also, general relationships regarding power spectral density estimates as a function of the skewness and kurtosis of the data record are discussed.
Analytical simulation and experimental measurement of stress wave propagation in guided projectile structures
Authors: Anderson D. M. , Hanse J. G. , Helvig T. N.
Published: October 2005

An analytical simulation and experimental measurement of stress wave propagation through a guided projectile structure was made and the results correlated through the use of fast Fourier transform (FFT) methods. Two guided projectile structures were simulated; one with and one without bolted joints such that signal attenuation across a joint could be evaluated. The analytical simulation consisted of a linearly elastic finite element structural model subjected to a time-history force input and solved using SAP IV via direct integration of the coupled differential equations. The experimental measurements were made using a pulse-testing technique wherein a structure was instrumented with accelerometers and impacted with a force input and the accelerometer response and force input measured. The resulting time history response data, whether analytical or experimental, was then analyzed using FFT methods to generate a frequency domain representation of the response signal for comparison. Results indicate finite element structural simulations of elastic stress wave propagation are a valid design tool for studying the noise characteristics of a structure being impacted with low order force inputs. [Work sponsored by Honeywell Independent Development Funding.]
Synthesis methods for an antivibration filter that is required to support the source mass
Authors: Putnam C. B. , Rowlands R. O.
Published: October 2005

Classical network synthesis theory, that was developed for the design of electrical filters terminated in a resistance, may be applied to the design of anti-vibration mechanical filters, except when the filter has to support the source mass. A modified design method has been developed to produce a termination consisting of a damped spring. Two cases are considered: (1) when the mass of the source is small, it is incorporated in the design as the first reactive arm of the filter, and (2) when the mass is large, the design is first performed assuming the source mass to be the infinite and then modified to take into account the finite value of the mass. [Work supported by Naval Sea Systems Command.]
Preliminary analysis of tracked vehicle dynamics
Authors: Galaitsis A. G. , Remington P. J. , Norris T.
Published: October 2005

A simplified model has been adopted to describe the nonlinear track/sprocket and track/idler interaction of a tracked vehicle. The differential equations of motion were obtained through the Lagrangian formulation and the time history of displacements and forces were computed by finite difference techniques. The predicted forces and measured force-to-noise transfer functions were, subsequently, used to project the interior vehicle noise which compares favorably to date. [Work supported by U. S. Army Contract DAAD005-76-C-0748.]
Synthesis of English monosyllables by demisyllable concatenation
Authors: Lovins J. B. , Fujimura O.
Published: October 2005

The use of demisyllables plus voice-assimilated phonetic affixes (/− s, − z, − t/, etc.), rather than segments or syllables, as the basic units in speech synthesis would have important advantages [O. Fujimura, J. Acoust. Soc. Am. 59, S55(A) (1976)]. We have tested the practicality of such a model for monosyllabic words of English, using an inventory of demisyllables with a variety of nonaffixed clusters and syllable nuclei. Each initial demisyllable is prepared so as to include a constant length of the transitional portion, and nucleus length variations dependent on the final consonant(s) are automatically included in the “vowel” portion of the final demisyllable. Syllable nucleus “coloration” by postvocalic nasals, /r/, or /l/ is also found to be automatically accounted for in this scheme. For example, the initial demisyllable excised from CVC may be joined with − VN to make a natural-sounding CVN syllable. These experiments used both a parallel-type formant analyzer—synthesizer [J.P. Olive and M.J. Macchi, J. Acoust. Soc. Am. 58, S23(A) (1975)] and an LPC processor, with some retouching, and with minimal smoothing across the concatenative boundary of the parameters.
Rule-generated pitch contour algorithm based on Junction Grammar linguistic model
Authors: Millett R. , Melby A. , Strong W. J. , Lytle E. G.
Published: October 2005

A computer algorithm to generate pitch contours for various readings of an utterance is described. A Junction Grammar model of language containing semantico-syntactic information represented in “junction trees” is used as the basis for the algorithm. Recent developments of this model [Lytle, “Junction Theory as a Base for Dynamic Phonological Representation,” Reported of BYU Linguistics Symposium (Provo, UT, 1976)] have provided a means for going from “junction trees” to “articulation trees” which contain language-specific segmental and prosodic information. These “articulation trees” were used to generate a pitch contour for various readings of a sentence using one set of LPC analysis data. From a varied corpus of 10 sentences (10 LPC sets), 23 different readings were synthesized using the algorithm to generate the pitch (fundamental frequency) contour in each case. Current research shows favorable preliminary results in expanding the algorithm to also predict pause and duration parameters in a word concatenation speech synthesis system.
Fundamental frequency by rule for a text-to-speech system
Authors: O'Shaughnessy Douglas
Published: October 2005

An algorithm for the generation of fundamental frequency (F0) in a speech synthesis-by-rule system is presented. It accepts as input: syntactic information (part of speech of each word, and a surface tree representing the syntactic structure of the sentence) and lexical information (number of syllables and location of the lexically stressed syllable in each word, and simple phonemic information, such as: vowel versus obstruent versus sonorant, unvoiced versus voiced). In the overall system, such information is provided by parsing, lexical decomposition, and letter-to-sound rules. The output of the F0 algorithm is a sequence of F0 values, one every 10 msec, used in synthesizing the voiced portions of the output speech. The algorithm makes use of research findings of the relationship of F0 movements to the linguistic content of sentences. Such factors as stress, syntactic phrases, and sentence-type have direct F0 results: parts of speech and syntactic boundaries affect the degree and direction of F0 movements, respectively, and questions have rising terminal F0 and high F0 throughout.
Structure of a complete text-to-speech system
Authors: Allen Jonathan
Published: October 2005

The structure of a complete text-to-speech system, including lexical lookup, morphological analysis, parts-of-speech determination, parsing, letter-to-sound rules, lexical and phrase-level stress, morphophonemic rules, pitch and timing rules, and phonemic synthesis is presented. The interrelation of these processes is stressed, and the current status of the algorithm is described in relation to the quality of the speech output. Practical implementations (e.g., in computer terminals, or reading machines for the blind) are also presented, including special purpose hardware. The design of these specialized devices is shown to be related to the structure of the algorithms to be implemented.
Determination of articulatory parameters of the human vocal tract from acoustic measurements
Authors: Möller W. J. , Atal B. S. , Schroeder M. R.
Published: October 2005

Previous work [B.S. Atal, J. Acoust. Soc. Am. 55, 384(A) (1974)] established that the articulatory parameters of a vocal tract model can be calculated from appropriate parameters of its acoustic output (such as linear predictor coefficients). The method is based on a “nonlinear” regression analysis involving both the acoustic parameters and their products. The weighting coefficients for the regression were determined in a “training session” in which the vocal tract assumed, successively, several thousand different configurations. The method is now being applied to human speech using x-ray data obtained by Fujimura, Miller, and Kiritani [J. Acoust. Soc. Am. 58, S40(A) (1975)]. Preliminary results on estimating the height of the velum will be reported.
Growth patterns of the peripheral axons of the spiral neurons in culture
Authors: Sobkowicz H. M. , Rose J. E. , Bereman B.
Published: October 2005

Segments of the organ of Corti with its innervation preserved were excised from the newborn mouse and studied in culture. The following growth patterns were observed: (a) maintenance of the normal innervation pattern and growth along normal lines if the hair cells remain in their usual location, (2) growth by elongation of the fiber if the hair cells migrate into the out-growth zone and if the fiber remains in contact with the receptor, and (3) free growth of the fiber if its connections with the hair cells are broken. Growth by elongation is confined to the area of hair cell displacement. The growth is well organized and the length of the fiber compensates strictly for the distance the respective hair cell has migrated. Free growth proceeds at a faster rate then does growth by elongation, is independent of the receptors, is unrestricted in length, and uncontrolled in amount. The growth is disorganized and luxuriant for at least several weeks after explanation. [Work supported by NIH grants NS08626 and NS12732.]
Horseradish peroxidase ototoxicity
Authors: Ross M. , Nutall A. , Wright C. G.
Published: October 2005

Following intracochlear perfusion of horseradish peroxidase (HRP) in artifical perilymph (1% for 10 min–4 h; 1–24 survival), HRP was demonstrated histochemically in some hair cells and supporting cells, the basilar membrane, spiral limbus and stria vascularis of 18 anesthetized (DIAL) guinea pigs. No neuronal retrograde transport occurred. To test for possible HRP ototoxicity, cochlear microphonics (CM) were recorded during presentation of two pure tones (4 kHz, 500 Hz) in four HRP experiments and two controls perfused with artificial perilymph alone. Only six drops of perfusate were used in one HRP and one control animal. No significant variation in CM occurred during perfusion. At stop-flow, CM declined slightly but soon stabilized in both 6-drop animals; decline was greater upon stop flow of either perfusate at one hour, but was greatest after HRP. An animal was then perfused with 10% HRP for one hour; CM declined during perfusion and continued downward at stop flow. Our results indicate ototoxicity of HRP, especially when concentrated, perhaps due to an adverse effect on inner ear fluid balance. Studies which utilized HRP as a tracer in the cochlea should be reassessed.
Permeability of cochlear partition to potassium and sodium ions
Authors: Konishi Teruzo , Walsh P. J. , Hamrick P. E. , Yankwich A. H.
Published: October 2005

Permeabilities of guinea pig cochlear partitions were determined by perfusing scala vestibuli (SV) and/or scala tympani (ST) with artificial perilymph with or without Na22 and K42 tracers. All concentrations of tracers were measured by gamma ray spectrometry. Perfusions ranged from 5 to 60 min at a rate of 2 μl/min. Under these conditions stimulus-related responses and endocochlear potential were not greatly suppressed. Perfusions were performed under the following conditions: perfusion of both SV and ST with tracers, perfusion of SV with tracers and ST without tracers, and perfusion of SV without tracers and ST with tracers. Results were similar under all the above conditions with concentration of K42 in endolymph becoming greater than in perilymph after 5 min of perfusion and becoming five times greater after 30 min of perfusion. On the other hand Na22 concentration is endolymph was less than 2% of that in perilymph for all perfusion times. Perfusion of SV and ST with 10−4 M ouabain or under anoxia resulted in a decrease of K42 and an increase of Na22 concentration in endolymph. These findings suggest that active transport of K into endolymph is through stria vascularis.
Effects of putative transmitters on afferent cochlear transmission
Authors: Bobbin R. P.
Published: October 2005

Putative transmitters and related substances were perfused through the guinea pig scala tympani while monitoring compound action potentials (AP) of the cochlear nerve and cochlear microphonics (CM). The following substances had no effect on the CM or AP when applied at 10 mM: GABA, glycine, L-alanine, β-alanine, histamine, norepinephrine, taurine, dopamine, and sodium acetate. Substances which had no effect on CM or AP at 1 mW but reduced the AP at 10 mW were glutamate, aspartate, citrate, 5-hydroxytryptamine, tyramine, and bicuculline methiodide. At 1 mM, the prostaglandins E1, E2, and F2α reduced the AP with no effect on the CM while F2β and A1 had no effect on the AP or CM. The mechanisms underlying the action of these substances is unknown. However, the results seem to eliminate some substances as afferent transmitters and suggest others. [Supported by NIH, USPHS Grant NS-11647-02.]