bluuebunny/crossref_metadata_2025 huggingface dataset:
Reactive ion etching of a 20 nanometers tungsten gate using a SF6∕N2 chemistry and hydrogen silsesquioxane hard mask resist
Authors: Larrieu Guilhem , Dubois Emmanuel
Published: October 2005

This article reports on a direct method for patterning a tungsten gate in the decananometric range using high-resolution electron-beam lithography and reactive ion etching (RIE). Electron-beam lithography is based on the use of hydrogen silsesquioxane for its remarkable properties as a negative-tone resist, for its high resistance to dry etching and its capability to deliver extremely straight sidewalls. The transfer of the resist pattern into the tungsten gate stack is ensured by RIE based on a chemistry using sulfur hexafluoride and nitrogen. An optimization of the tungsten etching step is performed by investigating the impact of the RIE power, gas flows, and pressure on both the anisotropy and selectivity with respect to silicon dioxide. Finally, the integration of a p-type metal-oxide-semiconductor field effect transistor with a tungsten gate and platinum silicide Schottky source∕drain was demonstrated and characterized to show that current-voltage characteristics do not exhibit symptoms of plasma-induced damage.
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pixel magnetic focus field emitter array image sensor with high-gain avalanche rushing amorphous photoconductor target
Authors: Egami N. , Nanba M. , Takiguchi Y. , Miyakawa K. , Watabe T. , Okazaki S. , Osada K. , Obara Y. , Tanaka M. , Itoh S.
Published: October 2005

A 50×50μm pixel field emitter array image sensor with a highly sensitive avalanche-mode photoconductive target and a scanning electron focusing system consisting of permanent magnets were fabricated and tested as a step toward the development of ultrahigh-sensitivity compact image sensors for high-definition television cameras. The experimental results revealed that the magnetic focusing conditions of the prototype sensor were in accordance with those estimated from the simulation, and the prototype sensor could obtain both enough resolution for its pixel size and high sensitivity by focusing the electrons emitted from the field emitter array onto the highly sensitive photoconductive target.
Highly anisotropic gate electrode patterning in neutral beam etching using F2 gas chemistry
Authors: Noda Shuichi , Hoshino Yasuyuki , Ozaki Takuya , Samukawa Seiji
Published: October 2005

Pure F2 gas chemistry was evaluated in comparison with SF6 and Cl2 gas chemistries for etching poly-Si gates of metal-oxide-semiconductor field effect transistors in our neutral beam source. In the case of SF6 gas chemistry, the polycrystalline silicon (poly-Si) etch rate was high enough, whereas a large side etching was observed. In the case of Cl2 gas chemistry, the pattern profile was anisotropic, but the etch rate was very low. The tradeoff was caused by differences in the etching reactivity of F and Cl radicals with the poly-Si. Though the SF6-based neutral beam caused a large side etching due to diffused F radicals, an anisotropic profile was obtained by using the F2-based neutral beam, and the etch rate was much larger than that in the Cl2 gas chemistry. These notable characteristics were accomplished by suppressing excessive dissociation of F radicals and by generating large amount of negative F ions in a pulse-time-modulated F2 plasma in the neutral beam source.
Synthesis and characterization of one-dimensional WO2 nanorods
Authors: Ma Yuan-Ron , Lin Chi-Ming , Yeh Chun-Liang , Huang Rong-Tan
Published: October 2005

One-dimensional (1D) WO2 nanorods were synthesized by hot-filament metal vapor deposition at high-pressure Ar flow without using any catalyst. The 1D WO2 nanorods grew on the roots and were a few micrometers long and 50–100nm wide. The x-ray diffraction pattern shows that the as-synthesized 1D WO2 nanorods are the monoclinic structure in space group P21∕c, and the roots are the β tungsten crystal of the cubic structure in space group Im3m. Field-emission-gun transmission electron microscopy images and selected-area electron diffraction patterns further confirm that the monoclinic 1D WO2 nanorods consist of the (011) planes and preferentially grow along the ⟨01¯1⟩ direction. According to these results, an uncatalyzed vapor-solid process is suggested to be the mechanism of growth of the as-synthesized 1D WO2 nanorods. In comparison with the Raman scattering of three-dimensional WO2 bulk powders, the Raman bands of the 1D WO2 nanorod are blueshifted and narrower, indicating phonon confinement associated with the 1D WO2 nanorod.
Profile evolution of Cr masked features undergoing HBr-inductively coupled plasma etching for use in 25nm silicon nanoimprint templates
Authors: Olynick Deirdre L. , Liddle J. Alexander , Rangelow Ivo W.
Published: October 2005

In nanoimprint template fabrication, the profile of the template features plays a significant role in the profile, release properties, and CD of the imprinted features. We present a study of profile evolution of nanopatterned Si etching for the fabrication of Si nanoimprint templates using a thin Cr hard mask and an HBr inductively coupled plasma (ICP). In this work, we show the effects of chamber pressure, line spacing, mask selectivity, and mask shape on the bowing, notching, microtrenching, and etching rate of nanopatterned silicon for pressures in the range of 2–10mTorr for line sizes between 20 and 100nm (1:1 line to space ratio). We observed that, for features with sizes below 50nm, increasing pressure leads to positively sloped sidewalls and microtrenching. At lower pressures, lower etching rates are observed—together with poorer selectivity and mask faceting. Furthermore, we see a tendency for aspect ratio dependent etching (ARDE) or reactive ion etching (RIE) lag at low pressures. Unlike RIE reactors, dc bias in our ICP etcher decreases with decreasing pressure and constant electrode and ICP power. This suggests that neutral shadowing is the mechanism responsible for ARDE. Under constant power and temperature conditions, due to counterbalancing pressure effects between 2 and 10mTorr, we obtain optimum imprint profiles at an intermediate pressure of 5mTorr.
Prevention of Cu degradation using in situ N2 plasma treatment in a dual-damascene process
Authors: Tomohisa Shingo , Yoshikawa Kazunori , Yonekura Kazumasa , Sakamori Shigenori , Fujiwara Nobuo , Tsujimoto Kazunori , Nishioka Kyusaku , Kobayashi Hiroshi , Oomori Tatsuo
Published: October 2005

The surface state of copper after an etching process using CF4 gas has been analyzed. Copper surface stability against corrosion is evaluated through a storage test performed under high-humidity conditions after the etching process. The storage test reveals that the copper surface suffered from both corrosion and oxidation. The copper degradation is caused by a postreaction between moisture and residual fluorine, wherein the resulting oxygen-containing copper film features a rough surface morphology. We examined in situ plasma treatments with several gases to reduce corrosive reactions. Results indicate that in situ N2 plasma treatment removes fluorine residue from the copper surface, and that this treatment effectively stabilizes the copper surface against corrosive conditions.
Influence of process variables on electron beam chemical vapor deposition of platinum
Authors: Beaulieu D. , Ding Yong , Wang Z. L. , Lackey W. J.
Published: October 2005

Electron beam chemical vapor deposition was performed in a modified environmental scanning electron microscope to deposit platinum structures. Process variables including voltage, beam current, deposition time, dwell time, and line time were studied in statistically designed and analyzed experiments on fiber (pillar-like structures) and line (wall-like structures) deposition. Deposition rates and geometric features such as aspect ratio were optimized. Results from the experimentation showed the importance of the beam current, voltage, and adsorbate replenishment to the deposition process. Growth rates up to 0.9μm∕min were obtained for short deposition times.
Cap layer induced stress in InAs∕(Al)GaAs quantum dots
Authors: Chen Shen-De , Chen Ying-Ying , Lee Si-Chen
Published: October 2005

Photoluminescence (PL) of self-assembled InAs quantum dots (QDs) on GaAs substrate with different In(Al)GaAs cap layer are studied. It is now well known that the peak position of the InAs QDs covered with InGaAs layer shifts to longer wavelength than those covered with GaAs and AlGaAs. The theoretical simulations are developed to distinguish various contributions to the wavelength shift from the dot height, strain, and barrier height of different cap layers. It reveals that most of the stress in the InAs QDs comes from the upper GaAs cap layer.
Transient interaction of spherical acoustic waves, a cylindrical elastic shell, and its internal multidegree-of-freedom mechanical systems
Authors: Huang H. , Lu Y. P. , Wang Y. F.
Published: October 2005

The transient interaction between a spherical acoustic wave and an elastic cylindrical shell containing an internally attached multidegree-of-freedom mechanical system is investigated within the limits of linear theory. Numerical results are obtained for the transient response of a spherical pressure-wave excited submerged shell containing a two-degree-of-freedom mechanical system. The interaction problem was solved using integral transform techniques. Both a series solution and an asymptotic solution for early time interaction were obtained, and good agreement was obtained between these two solutions.
Scattering function measurements for a 7-NM propagation range in the Florida Straits
Authors: DeFerrari H. A. , Nghiem-Phu Lan
Published: October 2005

A pulse received after transmission through the ocean will be spread in time owing to multipath and shifted in frequency owing to scatter from the ocean wave surface. If the time spread is small compared with the period of the surface waves, a Doppler spectrum may be measured for each successive part of the received signal. The resulting scattering function is a three-dimensional description of the transmission (intensity, frequency, and delayed time of arrival). Scattering functions for the 7-NM range show that energy arriving via SRBR paths has a Doppler spectrum with sideband components at surface wave frequencies. A large fraction of the total received energy is transmitted by RBR paths and is not influenced by surface waves. Measurements are presented for some environmental conditions typical of the Florida Straits. Results are compared with predictions from combined propagation and scattering models that include the effects of multiple scattering along the propagation paths.
Hydrophone calibrator for shipboard use
Authors: Hugus G. D. , Groves I. D.
Published: October 2005

The USRD type G40 calibrator is a shipboard system for conveniently calibrating hydrophones and their associated measuring systems by the comparison method in the frequency range 25–1000 Hz. This system provides isolation from mechanical deck vibrations and ship roll or pitch, and it can generate sound pressure levels from 130 to 190 dB re 1 μPa from 0.22- to 22.3-V driving signals.
Lateral waves from a continuous transition layer
Authors: Jones Hermenzo D.
Published: October 2005

An exact integral expression is given for the velocity potential produced by a harmonic point source located in a semi-infinite isovelocity space. A transition layer separates the source region from a second constant-velocity layer. A depth-dependent sound speed with two adjustable parameters is employed for the transition region. The velocity potential for the lateral wave is obtained using the method of steepest descent. The results are in agreement with those for the special case of the linear transition layer.
Theory and construction of multivariate Gaussian surfaces
Authors: Schuetz Luise S. , Zipfel George G.
Published: October 2005

A procedure has been developed for the construction of random rough surfaces with statistics which approximate the ideal of multivariate Gaussian statistics with a prescribed spectrum. Estimates of the deviation of the sample surfaces from the ideal ensemble statistics are made. The procedure uses a fast-Fourier-transform algorithm to produce a numerical surface which is then used to construct a physical realization of the surface via a numerically controlled milling machine. The resulting surface is one which can be used in scattering experiments and the degree of conformity of its statistics to those of the ideal is well understood. The use of these surfaces will eliminate a major source of uncertainty in the interpretation of controlled experiments.
Peripheral auditory function in the platypus, Ornithorhynchus anatinus
Authors: Gates G. Richard , Saunders James C. , Bock Gregory R. , Aitkin Lindsay M. , Elliott Murray A.
Published: October 2005

Cochlear microphonic (CM) potentials were recorded from the round window of the monotreme Ornithorhynchus anatinus (platypus) in response to pure tones between 500 Hz and 20 kHz. A 1.0-μV threshold curve showed best sensitivity for the platypus at 5 kHz with a high-frequency roll-off of approximately 20 dB/octave and a low-frequency rolloff of approximately 15 dB/octave. Intensity functions obtained at 2, 6, and 10 kHz were essentially parallel over the range of intensities studied. The maximum cochlear microphonic amplitude, even at the most sensitive frequency, did not exceed 100μV. The intensity function obtained at 6 kHz, close to the best frequency of the animal, was linear over a 40-dB range, and passed through a maximum at approximately 90 dB SPL. Click responses showed a cochlear microphonic potential followed by two neural potentials analogous to the N1, N2 frequently reported in other species. This study lends support to the notion that the auditory system of the platypus is intermediate between that of reptiles and mammals.
Transformation function of the external ear in response to impulsive stimulation
Authors: Price G. Richard
Published: October 2005

Impulse noise presents great difficulties in the estimation of auditory hazard. As a first step in determining the energy that actually reaches the cochlea during impulsive stimulation, the transformation function of the external ear was measured in response to impulsive stimulation. A model of the human external ear and live cat ears instrumented with condenser microphones were exposed to gunfire and narrow-band acoustic clicks. In all cases the transformation function arrived at by Fourier transformations of the impulses matched reasonably well the transformations determined by pure-tone or 1/3-octave-band random-noise measurements. The rise time of the gunfire impulses had increased markedly at the eardrum position as compared with the open field. However, a damage risk criterion for impulse noise should probably account not only for the transformation function of the external ear, but for that of the middle ear as well.
Peculiar case of “voiceprints”
Authors: Hollien Harry
Published: October 2005

“Voiceprints,” a technique based on a traditional method of speech spectrography, is currently being used in criminal investigations and courts of law in an attempt to provide identifications of speakers from the recorded voice samples. This letter reviews (1) the social relevancy of the problem, (2) the relationship of “voiceprints” to the larger issue of speaker identification, and (3) the differences between laboratory experiments and forensic investigations. New perspectives are suggested relative to this controversy and related issues.
Measured variations in aircraft noise near Arlanda Airport
Authors: Kajland Anders R.
Published: October 2005

Tape recordings were made of ca 1500 takeoffs at Arlanda Airport by means of an automatically operating recording device. Type of aircraft and destination as well as temperature, air humidity and wind velocity, and direction were registered. Correlation analyses of peak sound levels in dBA and meteorological factors were made. Sound level showed no significant covariation with humidity and temperature, but a positive correlation to the wind velocity from the aircraft towards the measuring station was found. The mean values measured verify theoretical calculation of the sound level from standard noise contours according to ISO Recommendation No. 507 and NASA CR-767 and also show that calculations are more accurate than occasional measurements. Parts of the data were also analyzed as to the difference among dBA, PNdB, EPNdB, and dBD. High correlations among these different units were found.
Helicopter noise experiments in an urban environment
Authors: Kinney W. A. , Pierce A. D. , Rickley E. J.
Published: October 2005

In two series of helicopter noise experiments, sound-pressure-level recordings were made on the ground while a helicopter flew over (i) an array of microphones placed in an open field, and (ii) a similar array placed in the center of a city street surrounded by tall buildings. For given helicopter altitude and airspeed, it was found that the flyover noise recorded in the street, although initially lower, built up rapidly as the aircraft approached such that the peak recorded noise was actually more intense than that recorded in the open field. This result is in qualitative accord with the results of previous laboratory scale-model experiments performed by Lyon and Pande. The differences between the two sets of field data are attributed in major part to the fact that a reverberant sound field builds up in the street during flyover. This enhancement is less pronounced for higher flight altitudes. A simple theory based on geometrical acoustics and statistical concepts is described that quantitatively explains the sound enhancement found for a helicopter flying over a city street.
Reflection from a sinusoidal surface
Authors: Brownlee L. R.
Published: October 2005

A formula, derived for the scattering of the various orders, differs from the results of Eckart and Brekhovskikh in the same way as these results differ from each other—namely, by the term in front of the Bessel function. In our case the term is unity. By deducing a simple geometric formula for the angular distribution of scattered energy in the high-frequency limit, and by using an asymptotic form for the Bessel function, the three formulations are compared in the high-frequency limit at various values of height, angle, etc., with the geometric formula. The result is that our formulation agrees best.
Shallow-water bottom reverberation under downward refraction conditions
Authors: Cole Bernard F. , Podeszwa Eugene M.
Published: October 2005

In 1965, some propagation loss and reverberation level measurements were performed under downward refraction conditions at a location south of Long Island. The reverberation levels measured during those trials are reduced to scattering strength values by considering the details of the propagation to and from the bottom, and the results are shown to be similar to those that Urick derived by ignoring the details of the propagation paths. The manner in which downward refraction conditions facilitate the measurement of bottom scattering strength values for shallow-water areas is also discussed.
On thresholds for surface waves and subharmonics of an oscillating bubble
Authors: Hsieh D. Y.
Published: October 2005

A theory of the simultaneous excitation of surface waves and subharmonics of an oscillating bubble is presented. The threshold pressures are computed, discussed, and compared with the available experimental values.
Geographic patterns in volume-reverberation spectra in the North Atlantic between 33°N and 63°N
Authors: McElroy Paul T.
Published: October 2005

Volume-reverberation observations were made at 34 stations on Cruise 105 of R/V CHAIN during its passage from Newfoundland to the Azores, and thence to Portugal and Ireland. The acoustic returns at each station were analyzed in 16 1/3-octave bands extending from 1 kHz to 31.5 kHz to yield column strength spectra. Techniques to maximize the accuracy of these spectra are described. Representative spectra are plotted. Using a measure we have called the cross-standard deviation, we found evidence that the spectra for nearby stations were similar and thus could be classed in geographically-based groups called pelagic regions. This is reasonable since much volume reverberation is sound scattered from animals which in turn are distributed in pelagic faunal regions. We present a matrix showing the similarity of each pair of stations; a small number indicates similarity, while a large number indicates difference in the two spectra. We have identified many of these regions on the basis of physical-oceanographic features such as the polar front. These features are used in defining boundaries for the regions.
Sound radiation from a cylinder immersed in an acoustic fluid bounded by an elastic half-space
Authors: Skidan O. , Klosner J. M. , Baron M. L.
Published: October 2005

The problem of the forced steady-state response of an infinite cylindrical shell immersed in an acoustic fluid bounded by an elastic half-space is investigated. The solution is obtained by using the Helmholtz integral to express the acoustic velocity potential, utilizing the Fourier transform to determine the influence coefficients for the pressure-velocity relationship at the boundary of the half-space, and by using a modal analysis to express the shell response. By enforcing the appropriate boundary conditions at discrete points of the interfaces, a system of simultaneous equations is obtained. The solutions of these equations yield the values of the unknown source strengths which are then used to determine the pressure field.
Exact solution to finite amplitude oscillation of an anisotropic thin rubber tube
Authors: Shahinpoor M.
Published: October 2005

Based on the theory of finite deformations of homogeneous anisotropic materials of Ericksen and Rivlin and on the Truesdell theorem on quasi-equilibrated motions of incompressible, anisotropic materials, the problem of large-amplitude free and forced oscillations of a longitudinally anisotropic elastic thin rubber tube is analyzed. Exact expressions for the dynamic deformations are given upon solving explicitly the nonlinear, nonautonomous time-dependent differential equations of motion under the action of a blast load that decays linearly with time.
Wave analysis of sound decay in rectangular rooms
Authors: Yegnanarayana B.
Published: October 2005

The decay of sound in a rectangular room is analyzed for various boundary conditions on one of its walls. It is shown that the decay of the sound-intensity level is in general nonlinear. But for specific areas and impedances of the material it is possible to obtain a linear initial decay. It is also shown that the coefficients derived from the initial decay rates neither correspond to the predictions of Sabine's or Eyring's geometrical theories nor to the normal coefficients of Morse's wave theory. The dependence of the coefficients on the area of the material is discussed. The influence of the real and the imaginary parts of the specific acoustic impedance of the material on the coefficients is also discussed. Finally, the existence of a linear initial decay corresponding to the decay of a diffuse field in the case of a highly absorbing material partially covering a wall is explained on the basis of modal coupling.
Loudness discomfort level: selected methods and stimuli
Authors: Morgan Donald E. , Wilson Richard H. , Dirks Donald D.
Published: October 2005

Two investigations were conducted (i) to determine a reliable procedure for obtaining loudness discomfort levels (LDL) and (ii) to observe the effects of frequency on the LDL. Three psychophysical methods were compared in the measurement of the LDL—a programmed method of constant stimuli, the method of adjustment, and a tracking method. The method of constants provided the most reliable judgments over six trials for a 1000-Hz stimulus. The LDL was then measured utilizing the method of constants for pure tones at octave frequencies from 125 to 4000 Hz, and for a wide and narrow band of noise. The LDLs (in dB SPL) were highest at low frequencies (through 500 Hz) and relatively constant for 1000, 2000, 4000 Hz, and the wide-band noise. The relatively high LDLs in the low frequencies are explained on the basis of difference in the intensity level for low frequencies measured in a conventional 6 cm3 coupler and that observed in the ear canal when a supra-aural earphone is fitted on the head. When a correction is made for this difference the LDL results across frequency compared closely with results from loudness-contour studies.
Reception of consonants in a classroom as affected by monaural and binaural listening, noise, reverberation, and hearing aids
Authors: Nábělek Anna K. , Pickett J. M.
Published: October 2005

Reception of consonants was studied with normal-hearing subjects in a sound-treated classroom, at reverberation times T ≃0.3 and 0.6 sec, to compare binaural and monaural reception, with and without hearing aids, in the presence of an impulsive noise (16 imp/sec) and a quasisteady noise (a babble of eight voices). The consonants were spoken in words inbedded in a rapidly spoken carrier phrase. The speech and noise sources subtended an angle of 60° on a circle 11 ft in radius centered on the listener, to give a large advantage for binaural reception. Binaural gain was taken as the difference in speech-to-noise ratios for 60% correct reception comparing binaural and monaural results. The binaural gain at short reverberation, with unaided listening, was 5 dB in the presence of the babble and 4 dB in the presence of the impulsive noise. The introduction of hearing aids and the increase in reverberation each caused the binaural gain to decrease to 3 dB. The small increase in reverberation caused a substantial decrease in reception under the noise conditions tested. Analysis of the consonant responses to reflect reception of the phonetic features of voicing, manner, and place, for both initial and final consonants, indicated that the acoustic conditions of reverberation and binaural listening affected feature reception in predictable ways.
Sound radiation from a circular steel plate driven on the edge
Authors: Watson E. Eugene , Hannon Robert J.
Published: October 2005

Two scanning techniques are now being used to determine the vibrational patterns and farfield sound radiation of complex vibratory systems. One technique is a nearfield scanning apparatus which scans the vibrator and gives a three-dimensional display on graph paper of the modal patterns. The other scanning technique uses the principles of holography to locate farfield sound sources on the vibrator. Using these two scanning systems, sound radiation from a vibrating circular plate driven on the edge was studied.
Thermoelectric sound generation in water
Authors: Clynch J. R. , Thompson L. A. , Muir T. G.
Published: October 2005

The acoustic field of a thermodynamic disk subjected to an alternating electric current is described theoretically and experimentally. Experimental results for the variation of the sound-pressure level with frequency and electrical power and beam patterns are reported for a thin disk device. The experimental results agree quite well with the theory.
Wave theory of SOFAR signal shape
Authors: Guthrie K. M.
Published: October 2005

Wave theory is used to derive SOFAR signal shapes. Approximate analytical methods are not employed; the normal modes are obtained by direct numerical solution of the wave equation in measured oceanic velocity profiles. The dependence of signal shape on details of the velocity profile is demonstrated and anomalous signal shapes recorded in New Zealand waters are interpreted. The single zero-order mode is found to dominate as an energy carrier; this could account for some of the fluctuations in signal strength observed in long-range propagation trials.
Species differences in cochlear fatigue related to acoustics of outer and middle ears of guinea pig and chinchilla
Authors: Drescher Dennis G. , Eldredge Donald H.
Published: October 2005

After guinea pigs were exposed to octave-band noise, which in chinchillas produces behavioral threshold shifts of more than 50 dB, as well as significant shifts of cochlear microphonic potentials, only minimal changes in guinea pig cochlear microphonic responses were found. Differences in sensitivity to noise exposure between the two species could be accounted for by four factors. (1) At lower frequencies, the attenuation caused by the closed bulla is important up to frequencies which are higher for guinea pig than for chinchilla. (2) The resonance associated with sound-pressure transformation from tragus to tympanic membrane is observed at frequencies about an octave higher in the guinea pig than in the chinchilla. (3) Cochlear microphonics with sound pressure measured at the drum and the bulla opened are less sensitive for guinea pig than for chinchilla. (4) Departure from linearity and/or onset of distortion of cochlear microphonics occurs at sound-pressure levels which are different for guinea pig than for chinchilla. For frequencies less than about 5 kHz, to produce a criterion change in cochlear sensitivity the level of octave-band noise in the field must be 15 to 25 dB greater for intact guinea pig than for chinchilla.
Are two ears necessary for localization of sound sources on the median plane?
Authors: Hebrank Jack , Wright D.
Published: October 2005

Several investigators have shown that monaural localization of sound sources on the median plane (MP) is inferior to binaural MP localization, causing speculation that two ears are necessary for MP localization, and further, that two ears may allow binaural processing of asymmetrical pinna filtering making localization of unfamiliar sounds possible. The purpose of the two experiments reported in this paper is (1) to test the hypothesis that binaural subjects can localize unfamiliar sounds more accurately than monaural subjects, and (2) to evaluate monaural localization accuracy after training. The results show that binaural and monaural subjects have similar difficulty in localizing unfamiliar sounds and show that monaural subjects can easily be trained to localize as well as they normally localize with two ears. The results indicate MP localization is fundamentally a monaural process.
On the differences between localization and lateralization
Authors: Plenge G.
Published: October 2005

In recent years, it has become common use to distinguish between localization and lateralization, i.e., in the first case, we hear the sound as “out there” [outside-head localization (OHL)], and in the second as inside the head [inside-head localization (IHL)]. This paper deals with the assumption of a basic difference between OHL when listening to sound coming from an external source and IHL which, as generally reported, occurs when listening to sounds coming through earphones. Results of two experiments give evidence that OHL also occurs when the signals at both ears simulate an external source sufficiently alike, although these sound events are conveyed by earphones. These results prove that the question of whether OHL or IHL occurs does not depend on any kind of electroacoustic transmission.
Detection of binaurally masked tones by the cat
Authors: Wakeford Onslow S. , Robinson Donald E.
Published: October 2005

Detection of diotic and dichotic tones partially masked by noise was studied in the cat. The continuous noise masker was always diotic (N0). The single gated tone burst had a frequency of 0.5, 1.0, or 1.5 kHz, and was presented in phase (S0), 180° out of phase (Sπ), and monaurally (SM). The transducers were held in a fixed spatial relation to the auditory canal by means of “pinna inserts” and leather helmets. An avoidance response in a shuttle box was used to measure detectability. The cats displayed as large a release from masking in the Sπ condition at 1.0 and 1.5 kHz as at 0.5 kHz. At 1.5 kHz, the cats showed a greater release from masking than did the human observers studied under comparable conditions.
Cepstral and stationarity analyses of full-term and premature infants' cries
Authors: Tenold Janet L. , Crowell David H. , Jones Richard H. , Daniel Thomas H. , McPherson D. Frank , Popper Arthur N.
Published: October 2005

Pain cries elicited from nine full-term, clinically normal neonates and five premature neonates with no reported abnormalities were studied using computer analysis. Based on the source-filter theory of speech production, greater variability of fundamental frequency (F0) and of cry spectra were hypothesized for premature infants. The cepstral technique was used to extract F0 from the cry spectra of each infant. The null hypothesis of no differences in variability of F0 between groups was tentatively accepted. A Test for Stationarity was used to determine spectral variability. As predicted, results showed greater variability of cry spectra for premature infants. Spectral variability findings were interpreted as probably reflecting differences in underlying neurophysiological maturity.
Voicing contrast: perceptual and productive voice onset time characteristics of adults
Authors: Zlatin Marsha A.
Published: October 2005

This study was designed to examine the status of voice onset time (VOT) in identification and production of word-initial voiced and voiceless labial, apical, and velar stop consonants for 20 English-speaking adults. Synthetic speech stimuli were constructed for four continua including BEES/PEAS, BEAR/PEAR, DIME/TIME, and GOAT/COAT. VOT values for 30 productions of the same words examined in the identification task were determined from spectrographic measurements. Analyses of the perceptual data revealed significant differences among labial, apical, and velar stops for the VOT 50% crossover and lower and upper limits of the phoneme boundary, but not for boundary width. In production of voiced and voiceless stops, reliable differences for mean VOT were shown between all cognates and among places of articulatory constriction within voicing category. The latter finding was primarily related to the labial/velar comparisons. Variability among individual speakers was demonstrated in the percentage of voiced stops associated with VOT values in the lead portion of the continuum, whereas all subjects evidenced productions in the short lag range. Comparisons between identification and production demonstrated high consistency for VOT characteristics in that few productions coincided with the perceptual phoneme boundary or contrasting voicing category.
Diffuse-field technique for measuring directivity index
Authors: Bobber R. J.
Published: October 2005

The directivity index of three underwater sound transducers was measured by the diffuse-field technique and the value was compared with the results obtained by four other methods. Acceptable agreement was achieved only for frequencies above 25 kHz.
Acoustic fluctuations due to microbubbles in the near-surface ocean
Authors: Medwin Herman
Published: October 2005

Within several meters of the ocean surface there are enough ambient bubbles to create a distinctive microstructure with a dispersive acoustic index of refraction. In this region, the variation of total bubble-volume fraction produces fluctuations of the sound speed for frequencies less than about 25 kHz; the frequency spectra of these speed fluctuations are near Gaussian. However, perturbation of resonance frequencies of predominant bubble populations is the principal cause of fluctuations of the speed between 25 and 100 kHz; these fluctuations have frequency spectra that are imitations of the spectrum of the sea surface height which creates them.
Dynamic stability of a spherical shell in an acoustic medium
Authors: Lu Juinn-Fu , Popelar Carl H.
Published: October 2005

The dynamic stability of the forced breathing motion of an elastic thin spherical shell in an inviscid fluid of infinite extent is investigated. Only axisymmetric torsionless perturbations are considered. The kinematic nonlinearities are retained while the fluid is approximated by a linear acoustic medium. A stability criterion is developed and stability diagrams for a steel shell in water are presented. The acoustic reactance is responsible for sizeable shifts of the stability regions for the lower modes. Except in the neighborhood of resonance of the breathing motion, the acoustic resistance has little influence on the principal instability region. The nonlinear motion of parametrically excited modes is obtained by numerically integrating the equations of motion.
Comparative study of European concert halls: correlation of subjective preference with geometric and acoustic parameters
Authors: Schroeder M. R. , Gottlob D. , Siebrasse K. F.
Published: October 2005

We describe a subjective preference evaluation of European concert halls and attempt to correlate the subjective data with objective (geometric and acoustic) parameters of the halls. For the subjective evaluations, reverberation-free magnetic-tape recordings of a symphony orchestra are played from the stage of the hall and recorded at the “eardrums” of a specially designed dummy head with realistic surface impedance of the ear canal and pinnae. These recordings are electronically processed such that, when played back over two selected loudspeakers in an anechoic chamber, the recorded signals are recreated at the eardrums of a human listener. This method of recording and reproduction makes possible instantaneous comparison of the acoustic qualities of different halls under realistic free-field listening conditions on the basis of identical musical source material. Listeners of differing degrees of musical training make preference judgments of musical quality in paired-comparison tests. The raw preference data are subjected to multidimensional factor analysis yielding one “consensus preference” factor and several “individual difference” factors. Results are reported of correlations of the consensus preference with objective parameters of the halls (volume, width, reverberation time, initial time-delay gap, “definition,” and “interaural coherence”).
Tympanic muscle effects on middle-ear transfer characteristic
Authors: Nuttall Alfred L.
Published: October 2005

Using the cochlear microphonic potential from the basal turn as an indicator, changes in the magnitude and phase of sound transmission across the open-bulla middle ear of the guinea pig were determined for two levels of isotonic tympanic muscle contraction. Muscle action was produced by independent electric stimulation of the muscle bodies. Both the stapedius and the tensor tympani muscles attenuated the passage of low-frequency vibration giving the largest attenuation for frequencies below 300 Hz; the tensor tympani produced an attenuation of 28 dB or more; the stapedius produced 10 dB or more. For some frequencies, in the range 1 to 3 kHz, both muscles were capable of generating an apparent gain in transmission; the tensor tympani causing a gain of 5 dB at 2.5 kHz; the stapedius 0.5 dB at 2.5 kHz. The phase shifts of the cochlear microphonic potential relative to the sound stimulus were leading phase functions for all contraction cases. A second tympanic muscle contraction level, of lower magnitude, gave qualitatively similar but smaller results. Changes in the sound-transmission magnitude and phase were modeled with second-order low-pass system characteristics in which the break frequencies increase, the low-frequency magnitude decreases and the system becomes underdamped with muscle contraction. These transmission changes are accounted for in the model primarily by a decrease in the compliance of the middle ear, but small increases in resistance and inertance over the flaccid muscle state were also indicated.
Needed: a new definition of diffusion
Authors: Lyon Richard H.
Published: October 2005

The conventional definition of diffusion of sound in resonating systems has important major deficiencies. It is oriented toward acoustical spaces and is difficult to apply to the vibrations of structural systems. Second, it is impossible to reach the state of perfect diffusion in any finite space, and any reasonable metric of diffusion predicts finite system diffusion as very far from the ideal. Third, the definition applies only to systems of irregular geometry. A new definition of diffusion is proposed that would provide a continuous metric for finite systems, acoustical or otherwise, and approaches the current definition for very large irregular systems.
Traversing microphone spectroscopy as a means for assessing diffusion
Authors: Lubman David
Published: October 2005

Traversing microphone (TM) spectroscopy provides a rapid and sensitive means for assessing sound diffusion in rooms. TM spectra are power spectra obtained at the terminals of a small microphone during its traverse through a room at constant speed. The TM spectral shape is a sensitive indicator of the degree of directional diffusion. If the field is perfectly diffuse, the TM spectrum is precisely rectangular. Observed deviations from the ideal rectangular TM spectra are at once symptoms of imperfect diffusion and clues to their causes. The TM spectrum provides a measure of diffusion averaged over the path of traverse rather than at point locations. The present technique is limited to discrete frequencies. The frequencies must be moderate to high, since the path of traverse must be large in wavelength in order to obtain statistically stable results. Quantitative as well as qualitative assessments of diffusion may be possible with this promising new technique.
Diffraction by iterative ray-theory techniques
Authors: Hudimac Albert A.
Published: October 2005

The errors of a ray-theory solution of simple harmonic acoustic propagation in an inhomogeneous medium are shown to be corrected by radiation from a distribution of simple source whose density has the phase of the incident ray amplitude. In the case of singularities in the ray field, the density involves symbolic functions. The radiation from the distributed sources is obtained by iterative ray techniques based either on a Green's function formulation or an integral equation. An alternative technique uses an iterated artificial wavenumber. In an example, the modified ray-theoretic solution for lateral waves is given.
Atmospheric infrasound radiated by bridges
Authors: Donn William L. , Balachandran Nambath K. , Kaschak George
Published: October 2005

Constant-frequency infrasound (about 5 to 10 Hz for different sources) has been detected at a number of locations from different directions. In an intensive study of 8.5-Hz infrasound detected regularly at Lamont-Doherty Geological Observatory of Columbia University in Palisades, N. Y., positive sound fixes have been obtained at the Tappan Zee Bridge. Geophones placed at several locations on the bridge recorded vibrations of the same frequency. We conclude that the vibrational motions of bridges radiate infrasound into the atmosphere and that the infrasound is most readily detected during times when atmospheric wind and temperature structure favor acoustic channeling near the ground. The acoustic signal occurs in pulses having a duration which, although fairly constant on a given occurrence, may vary from a fraction of a minute to several minutes.
Turbulent spectral broadening of backscattered acoustic pulses
Authors: Brown Edmund H.
Published: October 2005

The analysis studies the broadening of the frequency spectrum of an acoustic plane-wave pulse backscattered into a finite-angle receiver by the action of a transverse mean wind which moves turbulent velocity and temperature fluctuations through the beam. The results include the frequency spectrum I(k) of the acoustic pressure as a function of wavenumber and the spectral equivalent width b, as a function of mean transverse wind speed and receiver aperture. For broad beams, both temperature and velocity fluctuations contribute to the apparent 180°-backscatter intensity, and the contributing eddy scales vary from λ/2 to λ/√2. Again for broad beams and for typical experimental parameters for atmospheric echosondes, the broadening effects of mean transverse wind in the scattering volume outweigh the broadening effects of turbulence trransported by a mean transverse wind during propagation to the scattering volume. However, as the receiver beam angle decreases, the spectral broadening drops to zero, regardless of mean wind. Figures are included to show the effects of wind broadening for the case of intermediate receiver beam angles.
Relationship of transducer apertures and separation distances to the directivity patterns in the nearfield region
Authors: Mikeska E. E. , McKinney C. M.
Published: October 2005

In many acoustic systems the aperture dimensions of the projecting and receiving transducers are comparable. The variation of received signal level with separation distance along the acoustic axis in the transition region between near- and farfields has been studied by several workers, but apparently little has been published on the directivity patterns for this case. This paper presents the results of an experimental investigation of the directivity patterns for a series of projector-hydrophone pairs of various ratios of apertures as a function of range from the nearfield to the farfield.
Time harmonic acoustic radiation from nonconcentric circular cylinders
Authors: Shaw Richard Paul , Tai George
Published: October 2005

A time harmonic pressure is applied at the inner boundary of an acoustic fluid body, composed of two parallel, nonconcentric circular cylinders, which is itself embedded in another infinite acoustic fluid. The resulting radiation is determined as an expansion in terms of the nonconcentricity. For an applied internal pressure in a j th spatial mode, each order of this expansion introduces a “nearest neighbor” mode, e.g., the first order requires a (j + i)th and a (j − i)th mode. The solution procedure is based on an expansion of the Helmholtz integral equation formulation.
Immersion apparatus for ultrasonic measurements in polymers
Authors: Hartmann Bruce , Jarzynski Jacek
Published: October 2005

An immersion apparatus for making ultrasonic measurements in polymers was constructed. A unique feature of this apparatus is that the specimen is held vertically, and the transducers are rotated in order to produce shear waves in the specimen. This arrangement allows measurements to be made through the melting point of crystalline polymers. Sound-speed measurements, accurate to ±2%, were made on 25 polymers at room temperature and on five of these polymers as a function of temperature. On 15 of the polymers, both longitudinal and shear sound speeds were measured. The longitudinal wave speeds ranged from 2820 to 1020 m/sec, while shear wave speeds ranged from 1230 to 650 m/sec. Using these sound speeds and measured densities, the elastic constants of these polymers were calculated. For four polymers elastic constants as a function of temperature were calculated.
Mathematical retroreverberation model
Authors: Nava M. Novoa
Published: October 2005

The reverberant response of hard-walled rooms to recycled excitation (“retroreverberation”) is analyzed by means of an electrical analogy theory. Solutions are found in the form of chains, a new link being added each time the excitation is recycled. The solutions describe the time dependence in both the onset and decay phases of the retroreverberation process. The solution is extended mathematically to the frequency domain, in which the method finds its most suitable expression. The physical applicability of the mathematical model has been established by experiments in a reverberation chamber. The experimentally observed temporal behavior of the sound field in the chamber has been predicted by use of the theoretical formula, and the time and frequency constants of the formula have been evaluated and interpreted. The work has provided justification of the initial ideas previously reported [see M. Novoa Nava, “Retroreverberation,” J. Acoust. Sec. Am. 53, 798(L) (1973)] and the basis for a quantitative method for measuring the time constants involved.