bluuebunny/crossref_metadata_2025 huggingface dataset:
Temporal fluctuation in community noise levels—a brief review
Authors: Sutherland Louis C. , Ollerhead John B.
Published: October 2005

Existing noise indices for evaluating community noise levels have usually included, explicitly or implicitly, some means of accounting for the inherent temporal variation that normally exists in outdoor noise environments. Some of the physical characteristics of these temporal fluctuations are considered with emphasis on fluctuations observed near highways. Alternative ways to describe these fluctuations are discussed, including application of fluctuation spectra which cover the frequency range of roughly 1–1000 MHz. Some of the conflicting evidence as to the potential subjective response to fluctuating noise levels is also considered.
Computer-aided collection of demographic data within day-night-level contours around airports
Authors: Seidman H.
Published: October 2005

In recent years computer models have been developed that make it possible to calculate the day-night levels around airports at a reasonable cost. Determining the number of people exposed to various noise levels has always been a time-consuming and expensive operation because it required extensive manual data gathering. This paper discusses how the output from an airport noise prediction model (NOISEMAP) has been modified so that the output is suitable as input into a commercially available computer program that automatically collects demographic data within an arbitrary polygon. A discussion of how the information produced can then be used in environmental impact reporting is given. This includes using the fractional impact method for defining impact.
Ultrasonic and Brillouin scattering study of some amino acids in aqueous solutions
Authors: Inoue N. , Ohno K.
Published: October 2005

The ultrasonic absorption of 1-proline, 1-serine, and 1-arginine were measured in the frequency range of 3–90 MHz using an automatic recording ultrasonic spectrometer. Ultrasonic velocity was measured at 5 MHz using a single-crystal interferometer of a variable path, and hypersonic velocity was measured by Brillouin scattering. To study the reaction, appropriate pH values were achieved by the addition of NaOH. Ultrasonic absorption as a function of pH value in all amino acids show a maximum, and so it is considered that the obtained excess absorptions are due to proton transfer reaction. The observed spectra of 1-proline and 1-serine have been analyzed in terms of single relaxation behavior, and the rate constants and the volume change have been obtained. Ultrasonic absorption of 1-arginine show two relaxations due to α-amino group and β-guanidine group. In the latter one, the ultrasonic absorption α/f2 was constant below 90 MHz, and then the relaxation frequency would be in the far region above the present experimental frequency. Therefore, the ultrasonic velocity at 5 MHz was compared with the hypersonic velocity.
Light scattering study of vibrational relaxation in liquids of some heterocyclic compounds
Authors: Takagi K. , Negishi K.
Published: October 2005

Ultrasonic velocity and absorption were measured in liquid furan (C4H4O), thiophene (C4H4S) and pyridine (C5H5N) over a frequency range from 70 to 700 MHz with high-resolution Bragg reflection technique [K. Takagi et al., J. Acoust. Soc. Am. 62, 354 (1977)]. The results were described as vibrational relaxation phenomena. In furan and thiophene, all the vibrational modes relax in a single process at 120 and 320 MHz, respectively, at 20 °C. While in pyridine, two relaxation regions were found in a velocity dispersion curve up to 7 GHz, which was obtained in an experiment made cooperatively with Brillouin scattering. Quantitative analysis suggests that all above the third vibrational mode (605 cm−1) relax at 760 MHz, and the lowest (375 cm−1) and the second (405 cm−1) modes, at 3.9 GHz. This type of vibrational double relaxation has already been found in liquid benzene, dichloromethane, and dibromomethane.
Acoustic Measurement of Isotopic Concentration of Gases
Authors: Keolian Robert , Garrett Steven , Maynard J. , Rudnick Isadore
Published: October 2005

Two identical, thermally connected spherical resonators have been constructed to make accurate measurements of the isotopic concentration of He3-4He gas mixtures. One sphere is filled with pure He4, while the unknown mixture is placed in the other, Radial modes are excited in order to minimize viscous wall losses which reduce the quality of the resonance. A small cylindrical PVF2 driver at the center of each sphere selectively excites the radial modes, and electret microphones are used for pick-up at the walls. Measuring the ratio of the resonant frequencies gives the molecular weight ratio of the two gases. Phase-locked loop circuits have been developed for tracking the resonances and digital electronics are used for direct readout of the concentration. [Work supported by ONR and NSF.]
Ultrasonic excitation of a thin nematic disc
Authors: Hayes C. F.
Published: October 2005

A barium titanate crystal was used to excite a nematic liquid crystal with an ultrasonic wave of 1 MHz. The nematic sample was aligned by lecithin so in its unexcited state the optic axis was perpendicular to the glass walls of the sample. Nematic discs of various radii and thicknesses in the range of 0.1 and 0.01 cm, respectively, were investigated. It was found that modes of oscillation similar to those occurring in the vibration of a drumhead could be set up in the discs. However, the amplitude of oscillation of a drumhead is maximum in the center and minimum at the circumference with the opposite being true for the nematic disc with its radial boundary open to the air. The modes of the nematic were observed using a reflecting polarization microscope. The effect is attributed to acoustic streaming. Using the algebraic computer language REDUCE a theory has been developed to explain the pattern of oscillation and flow as well as the optical effects which occur. Flow patterns have been seen directly by observing the motion of small particles in nonliquid crystal samples such as water and oil. The value of the effect for visualization of acoustic wave fronts is noted. [Work supported by ONR.]
Acoustic cavitation prediction
Authors: Apfel Robert E.
Published: October 2005

In the course of preparing a chapter on “Acoustic Cavitation” for a volume on “Ultrasonics” for the series Methods of Experimental Physics [edited by P. Edmonds, Academic, New York], I noticed that the question of what type of acoustic cavitation occurs for a given set of circumstances could be displayed in a simple manner in a series of graphs. The ordinate scale of these graphs is the ratio of a particular bubble radius (see below) and the radius at which a bubble is resonant at a given frequency. The abscissa is the ratio of acoustic pressure amplitude to ambient pressure. Five relevant bubble radii are plotted: The radius associated with (1) nucleation, (2) the rectified diffusion threshold, (3) inertially limited growth, (4) the maximum size of a transient bubble, and (5) the initial size of a transient bubble that will assure supersonic collapse. When these are plotted on a single graph for a given frequency and equilibrium gas saturation pressure, regions are defined which allow one to predict under what conditions a given type of cavitation will exist and, for transient cavitation, whether it will be violent. [Work supported by Physics Program, U. S. Office of Naval Research.]
Effect of ultrasound on the heat conduction in metals
Authors: Fairbanks H. V. , Haider M. I.
Published: October 2005

The objective of this investigation was to study the influence of ultrasound having a frequency of 20 kHz upon the heat conduction of three metals: steel, aluminum, and magnesium. The variables used in this study included: ultrasonic intensity and temperature. The temperature measurements were taken along the length of the rod with a radiation thermometer. A continuous heat transfer system, computer modeling program was used to determine the change in the heat conductivity coefficient due to the introduction of ultrasound into the metal. It was found that insonation of the metals increased the thermal conductivity from 2.25 to 3.55 times. For iron, the higher temperatures used decreased the influence of ultrasound. Aluminum showed the greatest temperature difference between the nodes and antinodes in the metal bar during insonation, a higher temperature being produced at the antinode.
Negative group velocities of Lamb waves
Authors: Negishi K.
Published: October 2005

Negative group velocities, which mean that the direction of propagation of wave energy and that of wave phase are opposite, were found experimentally in S2 mode of Lamb waves excited on an A 1 plate of 1 mm thick at frequencies near 3 MHz. A stroboscopic schlieren technique was used to observe an ultrasonic pulse reradiated in water from the Lamb mode, together with specular-reflected and transmitted pulses. The phase velocity of the Lamb mode was derived from the angle of incidence, and the direction of group velocity was determined from the displacement of reradiated pulse relative to the specular reflection. Phase velocities observed at various frequencies were in good agreement with theoretical predictions, which also described negative group velocities appearing at phase velocities above 10 km/s. Such a high phase velocity is negligibly affected by water loading. Existence of negative group velocity seems inherent in S2 mode and independent of plate materials. Also in S4 mode, negative group velocities are predicted in a very narrow frequency range.
Multichannel cochlear prostheses: Noninvasive recording methods for estimating the spatial distribution of functional auditory nerve fibers and the spatial distribution of electrically excited nerve fibers
Authors: White M. W. , Merzenich M. M. , Vivion M. C.
Published: October 2005

Brainstem evoked response (BSER) techniques have been developed to study the electrode-nerve interface in cats implanted with intracochlear stimulating electrode arrays. These methods may be useful in measuring nerve and electrode function in prosthesis recipients. One method is used to estimate the stimulus current level at which neural excitation, generated by one electrode, overlaps the spatial excitation pattern generated by a second electrode. This technique is useful in determining whether each electrode is capable of exciting a restricted and unique sector of the auditory nerve. Initial experiments have confirmed that “The number of excited auditory nerve fibers versus BSER magnitude” can be estimated. Because “BSER magnitude versus stimulus current amplitude” can be noninvasively measured, “The number of excited fibers versus stimulus current amplitude” may be determined noninvasively. With this function and information from previous excitation mapping studies in the inferior colliculus, an estimate of “Fiber threshold versus cochlear place” can be made for most practical bipolar electrodes. [Work supported by NIH Grant ♯NS-11S04 and NIH Contract ♯N01-NS-7-2367.]
Defining optimum electrode arrays for multichannel cochlear prostheses; histopathological analysis
Authors: Leake-Jones P. A. , Merzenich M. M. , Vivion M. C.
Published: October 2005

The cochlear histopathology of two different deaf animal preparations was studied with light, transmission, and scanning electron microscopy. In one experimental series, cats were deafened by a slow injection of neomycin sulfate into the scala tympani immediately prior to an acute neurophysiological experiment. Brainstem evoked responses (BSER) indicated the loss of hearing was rapid. Histological examination revealed that all hair cells and many supporting elements of the organ of Corti were destroyed, with little decline in numbers of ganglion cells or dendrites. In a second series, cats were deafened slowly by daily intramuscular injections of neomycin. When the neomycin dosage was minimal for effecting complete hearing loss (detected by BSER) and survival times limited, dendrites and ganglion cells were nearly intact. However, in high-dose and/or long-surviving neomycin deafened cats, extensive loss of ganglion cells and dendrites occurs. These deaf animal preparations are suitable for electrophysiological mapping experiments designed to define optimum intracochlear multielectrode arrays, as they model different cochlear pathologies observed in profoundly deaf patients. [Work supported by NIH Contract ♯N01-NS-7-2367, NIH Grant ♯NS-11804, and Hearing Research, Inc.]
Organization of protection from the central nucleus of the inferior colliculus into the medial geniculate body of cat
Authors: Andersen R. A. , Roth G. L. , Aitkin L. M. , Merzenich M. M.
Published: October 2005

Orthograde tracer experiments were conducted to define, in detail, projections of the central nucleus of the inferior colliculus (ICC) into the medial geniculate body (MGB). Injections of 3H-1-leucine were introduced at physiologically defined loci within the ICC. The bilateral and spacially symmetrical projection was less dense to the contralateral MGB. The projection into the MGB formed a medial column passing rostrocaudally through the medial and deep dorsal nuclei; and formed a more lateral sheet passing rostrocaudally within the ventral nucleus and continuous through the lateral, transitional, and ovoidal subdivisions of the nucleus. Projections were topographically ordered within all labeled subdivisions of MGB. Bands of periodic light and heavy labeling were often seen approximately normal to the morphological laminations of the lateral division of the ventral nucleus. The basic pattern and topographic (cochleotopic) organization of the ICC projection into the MGB was indistinguishable from the pattern and topographic (cochleotopic) organization of the thalamocortical and corticothalamic projections. [Supported by NIH grant NS-10414 and Hearing Research Inc.]
Perceptual and physiological narrowband masking of low tones
Authors: Smith J. C. , Marsh J. T.
Published: October 2005

Two low pitch tones (140, 250 Hz) and three higher pitch tones (365, 500, 1000 Hz) were masked using four narrowband noise maskers. Threshold data suggest that the separation between center frequency of masker and tone frequency has less influence on the masking function for the two lower tones than for the three higher tones. These results were then compared with “physiological” masking of the farfield Frequency-Following Response (FFR) evoked by the middle (365 Hz) tone. The function thus obtained closely approached the perceptual masking function obtained for the two lower tones, but deviated, substantially, from the function characterizing the three higher tones. These results were interpreted as supporting the hypothesis that the perception of some low tones is mediated, in large part, by neural volleying. The reduced influence of noise center frequency on the masking of low tones suggests that these tones may be perceived through volleying of a diverse neuronal population. The mixed evidence surrounding the masking of the middle tone suggests a dual model for the perception of pitch over an intermediate frequency range. [Work supported by NIMH.]
Brainstem electric responses (BERs) in rhesus monkeys and humans
Authors: Peterson E. A. , Tanis D. C. , Drucker J. , Ginsberg B.
Published: October 2005

Waveform and latency of BERs elicited by filtered, monaurally presented clicks (major energy, 2.4–7.4 kHz) were determined for Rhesus monkeys, N = 6 (M. mulata) and humans N = 46. Similar measurement conditions were maintained for the two species. BERs derived from monkeys consistently displayed a greater number of identifiable components then did those of humans, particularly at moderate and high click intensities. Values of absolute latency and intercomponent latency difference were foreshortened in Rhesus monkeys compared to these values in humans. The magnitude of this relative foreshortening was found to increase with later components. Possible anatomic bases for the interspecific response differences observed will be discussed. [Work supported by EPA and NIEHS.]
Effects of perilymph collected during auditory fatigue on cochlear electrophysiology
Authors: Guth P. S. , Tachibana M. , Norris C. H. , Sewell W. F.
Published: October 2005

Previously we reported the release of auditory nerve activation substance (ANAS) into perilymph during sound stimulation [Soc. Neurosci. III, 11 (1977)]. Recently, experiments designed to increase the output of ANAS were carried out using more intense sound stimuli during the perilymphatic collection periods. In these experiments, compound VIIIth nerve action potentials and cochlear microphonics were measured. The more intense auditory stimuli caused reductions in these potentials reminiscent of auditory fatigue. Perilymph, collected during periods of auditory fatigue, when infused back into the guinea pig cochlea during silence caused reductions in cochlear potentials similar to those seen during auditory fatigue. Such cochlear electrical changes are not seen with perilymph collected during quiet periods. These results suggest that ANAS and/or another substance released during sound stimulation may be responsible for the changes in cochlear electrical activity seen during auditory fatigue. These results may point to a chemical basis for auditory fatigue and such related phenomena as temporary threshold shift. [Supported by NS ♯11647, The Veterans Administration Research Service and The John A. Hartford Foundation.]
Measurement of impacts in football
Authors: Reid Stephen E.
Published: October 2005

Actual impacts encountered by players were measured by telemetry during regulation football games. These data confirmed the fact that the manner of response to the blow rather than the blow itself determines the injury potential. Impacts to inanimate objects or to the heads of anesthetize animals produce experimental data that are simplified by the fact that the involved masses are constant and the contact time is negligible. On the football field, the players are tense at the snap of the ball and this resistance causes variable acceleration, variable forces, variable velocity changes as well as varying masses involved in these collisions. These measurements show that impacts on the field can not be compared with impacts involving bodies which are incapable of response. For example, a helmet under the test conditions of the laboratory is unable to withstand 90 ft lb of energy but the same helmet on the football field is exposed to far more energy when one considers that a 224 lb athlete with a speed of 100 yards in 10 s will deliver 3150 ft lb of energy. How such energy can be absorbed on the football field is demonstrated in this study by the physiologic response of the athlete alert to impending blows.
Ski vibrations and damping
Authors: Glenne B. , Porter D.
Published: October 2005

Vibrations and damping characteristics of skis are important with respect to the gliding, stability, and holding ability of skis which again affect skier safety. Some evidence exists that ski stiffness and ski weight also play a role in determining the term known among skiers as “ski damping.” This paper reports the vibratory properties of skis as measured in the laboratory and the field by using strain gage and LVDT transducers. Five well-known slalom skis are examined in the laboratory and results compared for one-dimensional bending vibrations. In the field, one alpine ski is analyzed for vibrations in bending, torsion, and sideflex under the most common ski maneuvers. When carefully tested in free vibrations, skis are found to conform fairly well with the accepted models of viscous free vibrations with logarithmic decrement damping. To obtain damping data over a wider frequency range (8–50 Hz) the skis were put on a shaker and magnification factors and resonance sharpnesses compared. Field testing show that hard snow conditions cause an entirely different vibratory response from that of soft snow conditions. Energy spectra obtained from field data show little peaking at natural harmonics except for sideflex vibrations under chattering ski conditions. This is thought to be due to the incessant forcing functions encountered under most skiing maneuvers.
Speech communication meets the IC revolution
Authors: Allen Jonathan
Published: October 2005

Rapid improvements in integrated circuit technology have made it possible for complex speech processing algorithms to be implemented in compact, real-time, low cost circuits. In this session, the evolution of this technology will be traced from early discrete-component systems up to current practice. In a complementary way, speech processing algorithms will be described structurally so as to reveal the opportunity for custom circuit designs. The session papers describe several such custom devices of wide utility for speech processing research and applications, including both speech analysis and synthesis. A projection of future integrated circuit capability will also be given.
A monolithic 512 point DFT processor
Authors: Pettengill R. C. , Bosshart P. W. , de Wit M.
Published: October 2005

A monolithic DFT processor has been designed using the chirp-Z algorithm. The 512 point transform has potential application in a low cost homomorphic vocoder as well as instruments for the spectral or Doppler analysis of acoustical signals. Connected as a peripheral it could greatly increase the throughput of a minicomputer based signal processing system. The integrated circuit measures 240 × 215 mils and includes the required amplifiers, filters, and multipliers for the chirp-Z algorithm. An external master clock and a read-only-memory are required to operate the chip. The design is easily modified to perform both a windowed or unwindowed, true or sliding DFT. The high functional density of this chip is achieved by the use of CCD transversal filters to perform the four required convolutions. A data recirculation feature allows the convolution required for either a true or sliding 512 point transform to be performed on a 512 stage filter. The pre and post multiplications are performed by four quadrant 10 bit multiplying digital-to-analog converters (MDAC's). The processor has been designed to operate at data rates of between 2 kHz and 2 MHz with 50 dB of dynamic range. [Work sponsored by U. S. Army Electronics Command.]
Flexible, high-performance speech synthesizer using custom NMOS circuitry
Authors: Caldwell Jim
Published: October 2005

A programmable digital signal processor (PDSP) intended primarily for speech synthesis applications has been developed using custom NMOS LSI circuitry. Key features include high speech quality, great flexibility, simple interfacing to standard microcomputers, low cost, low power, small size, and the stability of a digital processor. Because of extensive programmability, substantial computational power, and a selection of hardware configurations, the PDSP components can implement a wide range of vocal tract model structures at costs roughly proportional to performance. For example, the user can create a cascade formant synthesizer, a parallel formant synthesizer, a hybrid cascade/parallel formant synthesizer, or a lattice filter structure. Typical applications encompass fixed-vocabulary speech output devices, systems for translating unrestricted text into speech, and low-bitrate/secure voice communications. The custom devices are currently being designed into a high-performance speech output reading system for the blind.
Recognition Memory: Low cost content-addressable parallel processor for speech data manipulation
Authors: Lamb S. M. , Vanderslice R.
Published: October 2005

Associative memories for computers have heretofore been too costly, compared with conventional random access memories, for most applications. Recognition Memory (REM) employs a judicious blend of serial and parallel processing to make available at low cost most of the advantages not only of associative memory but also, more broadly, of what C. Foster calls Content Addressable Parallel Processors (Van Nostrand Reinhold, New York, 1976). REM accesses stored data by the content rather than the storage location addresses—though REM can be used in RAM mode with addressed read and write. There are six hardware recognition functions: memory locations can be made to respond if their contents, with respect to the presented comparand, match exactly (=), or are ≠, >, ⩾, <, or ⩽. These are combinable by Boolean operators in software. REM also has a multiwrite function whereby one instruction writes data into multiple locations—all responders to a prior recognize operation, say—and this, in combination with bit masking (available for all functions, including RAM-mode read and write) enables parallel arithmetic and other powerful CAPP operations providing speed, flexibility, and programming ease. REM is useful wherever conventional computers are required to do serial searches or template comparisons, especially with large data bases or high data rates. Applications for REM in real-time speech recognition—distributed processing for parameter tracking (fo, e.g.), feature extraction, and higher-level constraints—and large-vocabulary speech response units are discussed.
Calculation of the acoustic field generated by a moving source
Authors: Hawker Kenneth E.
Published: October 2005

This paper considers the problem of computing the acoustic field generated by a moving point source. In particular, the acoustic field is obtained in terms of the normal modes of a horizontally stratified ocean. The source motion is assumed to be uniform (unaccelerated), but is not restricted to be radial to the receiver. The structure of the Fourier inversion integral is carefully analyzed and an evaluation carried out by the method of stationary phase. The stationary phase point is explicitly computed as an expansion in powers of the ratio of the source speed to the mode group velocity. The resulting expression for the velocity potential is examined for Doppler effects for both instantaneous (modal) Doppler as well as Doppler determined by a finite bandwidth Fourier transform.
Practical values of low frequency sound attenuation in the sea
Authors: Browning D. G. , Simmons V. P. , Urick R. J.
Published: October 2005

Two low frequency attenuation mechanisms have recently been identified; a boron relaxation process and scattering from oceanographic inhomogeneities. It is now possible to obtain at least semiquantitative predictions of attenuation of sound in the sea for all frequencies of practical interest. Unfortunately, the available sonar slide rules are based on out dated or incomplete attenuation formulas. This paper suggests new engineering formulas based on present at-sea and laboratory data applied to realistic propagation situations. [Work partially supported by Naval Underwater Systems Center.]
Project JAGUAR: Modeling sound propagation through the confluence of two major currents
Authors: Novarini J. C. , Núñez A. L. , Browning D. G.
Published: October 2005

In the South Atlantic Ocean the cold Malvinas current flowing up from the South meets the warm Brazil current flowing down from the North off the coast of Argentina near Buenos Aires. The confluence of subtropical and subantarctic water masses results in a complex oceanographic regime. As a basis for a future measurement program, acoustic propagation predictions have been made for the region utilizing raywave and other modeling programs. Results are compared to a previous experiment conducted through the subtropical convergence near New Zealand [R. W. Bannister et al., J. Acoust. Soc. Am. 62, 847–859 (1977)].
A new definition for acoustic transition range with application to oceanic eddies
Authors: Scully-Power Paul D. , Nysen Paul A.
Published: October 2005

The classical definition for acoustic transition range is that range at which the propagation loss, neglecting absorption, changes from spherical to cylindrical spreading. For ray acoustics, a definition which provides more physical insight into the propagation characteristics is that range at which rays with N loops begin to overlap rays with N + 1 loops. Since for low and mid latitudes a tight empirical linear relationship exists between loop range and horizontal phase velocity for any given ray path in deep water, a simple deterministic expression for transition range can be obtained for a major part of the world's oceans. Application of this formulation to ocean eddies shows that for a source or receiver within a warm core eddy the transition range is increased, while for a cold core eddy the effect is opposite.
Shadowing of sound propagation by a seamount in the northeast Pacific
Authors: Ebbeson G. R. , Thorleifson J. M. , Turner R. G.
Published: October 2005

A series of propagation runs at 230 Hz were made over Dickins Seamount to determine the shadowing effect of the seamount on the sound propagation. Receiver depths ranged from 329 to 633 m with source depths of 18 and 184 m. For the shallow source depth the measured results over the seamount showed a marked increase in propagation loss when compared to a combination of measured and predicted results made over a flat bottom nearby. As indicated by ray tracings, maximum shadowing was observed when the source was in a position which enabled the seamount to intercept all the deep refracted rays. An increase in propagation loss was not apparent in the measured results for the deep source depth because most of the propagating energy was confined near the sound channel axis above the seamount.
A new facility for evaluation of open-plan acoustics
Authors: Norman R. S. , Hedeen R. A.
Published: October 2005

A new, open-plan acoustics facility has been constructed at Riverbank Acoustical Laboratory in Geneva, Illinois. The facility has been designed to evaluate materials used in ceiling of open-plan designs as well as landscape screen and masking system performance. The facility has gypsum board walls and ceiling with dimensions of 6.1 × 12.2 × 3.5 m high. A 0.76-m plenum is used for the suspended ceiling. As a reference condition, 152 mm fiberglass has been installed on the facility walls and in the suspended ceiling. The floor is covered with NRC = 0.25 carpeting. Reference screens have been constructed from plywood and fiberglass to achieve an NRC value of approximately 1.0. During initial evaluation of screens as barriers, NIC′ values ranging from 18.5 to 22.5 have been achieved using nonabsorbing and highly absorptive screens. Data are presented for each of the component materials as well as for the total facility. A simple computer program for the calculation of NIC′ is presented.
Optical hydrophone research in the Navy
Authors: Bucaro J. A.
Published: October 2005

A new class of hydrophones is currently being developed which utilize optical beams and interface directly to fiber optic transmission and processing links. These optical hydrophones are divided into two generic types: (1) fiber sensors, which utilize acousto-optic interactions in fibers, and (2) hybrid sensors in which transduction takes place in a device external to an optical fiber. The details of these sensors and their advantages and versatility will be discussed.
Transducer utilizing optical fiber for the observation of intracardiac pressure
Authors: Yasuda T. , Kobayashi K.
Published: October 2005

An intracardiac pressure transducer has been developed using an electrofiberoptic system. The fiberoptic catheter-tip microtransducer is so secure inherently from electrical shock hazards that it has been desired to apply this type of transducer to clinical use. In this paper, the designing method of the present microtransducer is theoretically studied, and the precise fabrication of its miniaturized diaphragm is described in detail. As a result, the optimum distribution of the fibers at the measuring tip can be determined. For the present transducer, the miniaturized diaphragm at the catheter tip is precisely fabricated by a photoetching technique. The corrugations on the diaphragm are theoretically designed by the theory of an anisotropic elastic thin plate. Cutting the diaphragms and engraving the corrugations can be performed by an etching process with a good reproducibility. The various characteristics of the present transducer has been examined by pressure calibration apparatus. From several data in the clinical uses, the present transducer has been found quite excellent for a catheter-tip micromanometer.
A hybrid fiber-optic transducer for detection of sound and vibration
Authors: Christian J. D. , Slonecker M. H. , Stowe D. W.
Published: October 2005

When coherent light from a He-Ne laser is passed through a short length of step-index optical fiber, a familiar speckle pattern is observed which corresponds to the distribution of excited fiber modes. We have configured such a fiber on an acoustical diaphragm. By measuring the variation of light intensity of selected mode groupings with a photodetector, sound pressure levels of 44 dB re 1 μPa were detected which corresponded to ambient room noise in a 1-Hz band. Measurements were conducted in the band from 500 Hz to 1 kHz. The device is sensitive, easy to fabricate, and can also be used to measure the modal excitation pattern of the diaphragm.
Effects of source motion on ground reflection effects
Authors: Chapkis Robert L.
Published: October 2005

Interference effects from ground reflections are different for moving than for stationary noise sources. These differences have not generally been taken into account in analysis of noise measurements of moving sources such as aircraft. Sound source motion affects measured sound pressure levels for two reasons. First of all, since sound travels with a finite speed, retarded time effects must be taken into account for both “real” sources and “image” sources. Secondly, since the pressure signal received at a microphone must be time-averaged to obtain sound pressure levels, the distance a source moves during the averaging time must be taken into account. Results of analyses considering those two effects are presented and compared with measurements. [Work supported by NASA Langley Research Center.]
Noise characteristics of two parallel jets of unequal flow
Authors: Shivashankara B. N.
Published: October 2005

Many jet noise suppression devices employ tubes, lobes, etc., to break up the flow. To understand the suppression mechanisms of these devices, a two-parallel jet model experiment was conducted. The three-dimensional noise field was mapped for the case when one jet was at a velocity of 1800 ft/s and total temperature of 1000°F (jet 1) and the other was at 1150 ft/s and 200°F (jet 2). Transverse mean flow profiles were also obtained at three axial stations. These experiments were an extension of the earlier work by Bhat [W. V. Bhat, AIAA Paper 77–1290, 4th Aeroacoustics Conference, Atlanta, GA, 3–5 October 1977]. The experiments showed that noise from a high velocity jet is reduced by placing a second jet of lower velocity parallel to it on the same side as the listener. The noise reduction is maximum on the lower velocity jet side of the plane containing the common diameter of the two jets. The noise reduction decreases as one moves around the jets from this plane. No noise reduction is obtained at approximately 70° to this plane. Mean flow profiles showed insignificant interaction up to five nozzle diameters of the first jet. From a detailed examination of the noise results and earlier jet noise source location studies, it is concluded that acoustic shielding is the dominant mechanism responsible for the observed noise reduction.
Noise radiation from interacting air jets
Authors: De Metz F. C. , Matis M. F. , Wilson J. L.
Published: October 2005

The mechanisms and scaling laws for noise radiated from interacting subsonic air jets have been studied experimentally. Simultaneous measurements were conducted of the velocity field and radiated pressure associated with interacting jets formed downstream of sharp-edged, multiholed orifice plates. The orifice plates, containing from 1 to 31 holes, were placed at the termination of a quiet 76 mm I.D. pipe air-flow facility. The characteristics of the broadband and tonal components of the radiated noise field are evaluated in terms of: (i) the orifice plate hole geometries and flow interactions, and (ii) the downstream jet features.
Correlation of combustor acoustic power levels inferred from internal fluctuating pressure measurements
Authors: von Glahn Uwe
Published: October 2005

In recent years, significant progress has been made in reducing the fan and jet exhaust noise generated by aircraft gas turbine engines. As these major noise sources were reduced, other noise sources were uncovered and constitute new acoustic thresholds or floors. One of the more significant of these noise sources is combustion-associated noise. Extensive measurements of fluctuating pressures have been obtained internally for a variety of combustors. These measurements include data taken both in component development rigs and in engines. The combustor configurations include can-type and annular-type combustors. Herein, acoustic power levels (OAPWL) inferred from the fluctuating pressure measurements are correlated for a wide range of operating conditions and chamber geometries. The primary variables include chamber size, number of fuel nozzles, combustion staging, combustion heat release rates, and chamber pressure and inlet temperature levels. With the present correlation, values of OAPWL can be predicted for a given combustor and by use of a generalized combustion noise spectral shape, available in the literature, the spectral content for the given combustor can then be provided.
Three-dimensional acoustic waves propagating in acoustically lined cylindrically curved ducts
Authors: Ko S.-H.
Published: October 2005

A theoretical study has been made of three-dimensional acoustic wave propagation in acoustically lined curved ducts with rectangular cross section. The acoustic lining considered here is a fibrous sheet mounted on a locally reacting core with impervious backing. The eigenvalue equations in both radial and axial directions were derived by matching the normal component of the particle displacement and the acoustic pressure on the acoustic line surface. For a given duct geometry and known acoustic lining admittance a computer program was developed to solve for the eigenvalues and to obtain the sound attenuation of the propagating waves in the lined curved duct. The sound attenuation was calculated by using the acoustic energy expression for the waves propagating in a curved duct with rectangular cross section. Theoretical results are presented for three-dimensional wave modes.
Synthesis of duct acoustics computer codes and test facilities
Authors: Beckemeyer Roy J.
Published: October 2005

Sophisticated computer programs for the analysis of acoustic propagation in flow ducts have been developed in recent years. These programs are typically capable of accounting for the convective and refractive effects of mean flows and boundary layers, as well as for the scattering and absorption effects of wall acoustic linings and duct nonuniformities. In concert with improvements in analysis capability, test facilities have been developed for conducting extensive experimental investigations of flow duct acoustic linings. This paper describes the evolutionary development of a specific example of such analytical and experimental capabilities and, furthermore, describes the recent and ongoing synthesis of these capabilities into a unified duct acoustics research tool.
Application of root-locus method to cavity resonance
Authors: Elder S. A.
Published: October 2005

A root-locus solution for the frequency lock-in problem has been obtained for a wall-mounted cavity in turbulent flow, oscillating at Helmholtz or depth-mode resonance. For case where acoustic wavelength is large compared to cavity mouth dimension, feedback takes the form of a simple transverse modulation by acoustic standing wave in the cavity. System gain is found to derive from periodic deflection of volume flow into the cavity from external fluid as in Type-I organ pipe oscillation. Unlike the organ pipe case, however, only downstream interface waves are observed, there being no boundary condition imposed on the slope of the interface at leading edge. Phase velocity of the interface wave is obtained from mean stream velocity profile, using linearized instability theory. System is capable of oscillation at frequencies both above and below resonance, the exact resonant condition being characterized by a stream-wise slot width (M-1/4) times the interface wavelength, where M is an integer. From a knowledge of the nonlinear orifice resistance characteristic, oscillation amplitude can be predicted as a function of slot width. [Work supported by a GHR contract with the Naval Sea Systems Command, administered by the David Taylor Naval Ship Research and Development Center, Carderock, Maryland.]
The auditory system of an allosaurus, a late jurassic therapod dinasour
Authors: McCandless Geary A. , Madsen James H. , Parkin James L.
Published: October 2005

Dissection of the cranium of an Allosaurus theropod dinasour yielded a complete brain case with an intact auditory and vestibular system. The specimens from this reptile are about 140 million years old and come from the Morrison formation of the late Jurassic period. The specimen revealed a cast of the brain and all the cranial nerves. The most unusual finding was a complete columellar ossicle approximately 5 in. in length and 2-4 mm in diameter. The footplate of the columella was still positioned in the round window nitch. Examination of the columella permitted estimation of the position of the position of the tympanic membrane. The petrified bone retained its fine morphology so well that thin sections of the columella show haversian canals as in fresh bone. The entire cochlea and semicircular canals were indentified. Anatomical determinations were made by natural fracturing, careful dissection by sand under air pressure, and by x-ray tomography. The comparative functional anatomy of this 30 ft reptile will be made with some present day reptiles and birds. Discussion relative to the potential auditory function of the Allosaurus will also be presented.
Tuning curves of frog amphibian papilla nerve by single cycle sine wave
Authors: Sugai T. , Ooyama H. , Yano J. , Sawada S.
Published: October 2005

Tuning curves (TCs) for sine wave tone bursts (BTCs) were compared with those (STCs) for single cycle sine wave (SSW) stimuli in auditory fibers innervating amphibian papilla of a frog. Three types of responses were differentiated. First parallel-sharp type had a sharp peaked BTC. At the CF of the BTC, threshold for SSW rose by 10–20 dB. Difference between thresholds decreased gradually until the two TC's coincided at certain points onwards from the CF. Second parallel-round type had a flat BTC and the two TCs differed little even at the CF. The presence of these two types with similar CFs suggests that resonance characteristics vary even within a limited area in the papilla. The third was a crossing type. The relation between the two TCs near the CF was similar to that in the first type. At high frequencies far from the CF, however, the STC was lower than the BTC. This observation may suggest that the peripheral inhibition by the succeeding waves of tone bursts interferes with the expected excitation by the initial part.
Correlation between the response selectivity of the auditory thalamic area of the green treefrog and call discrimination
Authors: Mudry K. M. , Capranica R. R. , Gerhardt H. C.
Published: October 2005

A neurophysiological investigation of the green treefrog, Hyla cinerea, was aimed towards revealing principles underlying call detection. This species was used since its vocal repertoire is not only limited and highly stereotyped, but also controlled behavioral tests have determined the critical parameters that these animals use for species-specific recognition. In this evoked potential study of the diencephalon, the auditory center was found to be maximally responsive to certain bimodal stimuli. Combinations of two tones with a low-frequency component around 600 Hz and a high-frequency component between 2000 and 4000 Hz evoked a potential which was larger than the sum of the potentials to the component tones separately thus revealing a nonlinear convergence underlying the processing of complex sounds. Behavioral studies verify that females respond optimally to playback of synthetic calls having these same bimodal frequencies. Furthermore, temperature changes lead to a shift in the frequencies for the convergent response in the thalamus and for the behavioral selectivity of the females. [Supported by NIH.]
Recognition of acoustically degraded song by birds
Authors: Richards D. G.
Published: October 2005

Bird song is degraded during passage through the environment by attenuation, amplitude fluctuation, and reverberation [R. H. Wiley and D. G. Richards, Behav. Ecol. Sociobiol. 3, 69–74 (1978)]. The song of the rufous-sided towhee contains a rapid trill, especially susceptible to reverberation, preceded by a tonal introduction relatively unaffected by the above sources of degradation. Experiments were conducted in the field with playback of recorded bird song, with and without artifically introduced degradation. The undegraded trill alone, and both the degraded and undegraded full songs elicited a strong response from the birds; the degraded trill alone elicited a significantly lower response (p < 0.01). Both degraded and undegraded introductions did not elicit responses significantly different from zero. The species-specific information is therefore contained largely in the trill, sufficient alone for species recognition when undegraded. The introduction, while not coding species identity, serves as an alerting note when the song is degraded by distance, allowing the bird to lower its threshold of detection for the following trill containing the species-specific information.
In vitro analysis of synaptic potentials and neuronal morphology in avian brain stem auditory nuclei
Authors: Rubel E. W. , Jackson H. , Hackett J. R.
Published: October 2005

Nucleus magnocellularis (NM) and N. laminaris (NL) of the avian brain stem are considered homologous to the mammalian AVCN and MSC, respectively. Field potential and extracellular unit recordings from in vitro preparations of the 8th nerve and brain stem of the chick reveal an organization identical to that recorded in vivo. Intracellular recordings in NM have revealed two separable types of unitary excitatory postsynaptic potentials (reversed by depolarizing current) in response to 8th nerve stimulation: a short duration, “fast” potential (2–3 ms rise time), and a long duration, slower, more labile potential (4–6 ms rise time). Intracellular injections of horse-radish peroxidase show that axons from NM cells course ventrally and then bifurcate, sending one collateral to the ventral neuropil of the contralateral NL and the other to the dorsal neuropil of the ipsilateral NL. Terminal arborizations, limited to a region of 10–20 NL cells and overlapping, correspond to the graded EPSP's recorded from NL in response to ipsi- or contralateral 8th nerve stimulation. [Work supported by NSF, NIH, and the Deafness Research Foundation.]