bluuebunny/crossref_metadata_2025 huggingface dataset:
Post-Training Cyclooxygenase-2 (COX-2) Inhibition Impairs Memory Consolidation
Authors: Teather Lisa A. , Packard Mark G. , Bazan Nicolas G.
Published: July 2002

Evidence indicates that prostanoids, such as prostaglandins, play a regulatory role in several forms of neural plasticity, including long-term potentiation, a cellular model for certain forms of learning and memory. In these experiments, the significance of the COX isoforms cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) in post-training memory processes was assessed. Adult male Long-Evans rats underwent an eight-trial (30-sec intertrial interval) training session on a hippocampus-dependent (hidden platform) or dorsal striatal–dependent (visible platform) tasks in a water maze. After the completion of training, rats received an intraperitoneal injection of the nonselective COX inhibitor indomethacin, the COX-1–specific inhibitor piroxicam, the COX-2–specific inhibitorN-[2-cyclohexyloxy-4-nitrophenyl]-methanesulfonamide (NS-398), vehicle (45% 2-hydroxypropyl-β-cyclodextrin in distilled water), or saline. On a two-trial retention test session 24 h later, latency to mount the escape platform was used as a measure of memory. In the hidden platform task, the retention test escape latencies of rats administered indomethacin (5 and 10 mg/kg) or NS-398 (2 and 5 mg/kg) were significantly higher than those of vehicle-treated rats, indicating an impairment in retention. Injections of indomethacin or NS-398 that were delayed 2 h post-training had no effect on retention. Post-training indomethacin or NS-398 had no influence on retention of the visible platform version of the water maze at any of the doses administered. Furthermore, selective inhibition of COX-1 via post-training piroxicam administration had no effect on retention of either task. These findings indicate that COX-2 is a required biochemical component mediating the consolidation of hippocampal-dependent memory.
Portal dose image prediction for dosimetric treatment verification in radiotherapy. II. An algorithm for wedged beams
Authors: Pasma Kasper L. , Vieira Sandra C. , Heijmen Ben J. M.
Published: July 2002

A method is presented for calculation of a two‐dimensional function, describing the transmission of a wedged photon beam through a patient. This in an extension of the method that we have published for open (nonwedged) fields [Med. Phys. 25, 830–840 (1998)]. Transmission functions for open fields are being used in our clinic for prediction of portal dose images (PDI, i.e., a dose distribution behind the patient in a plane normal to the beam axis), which are compared with PDIs measured with an electronic portal imaging device (EPID). The calculations are based on the planning CT scan of the patient and on the irradiation geometry as determined in the treatment planning process. Input data for the developed algorithm for wedged beams are derived from (the already available) measured input data set for transmission prediction in open beams, which is extended with only a limited set of measurements in the wedged beam. The method has been tested for a PDI plane at 160 cm from the focus, in agreement with the applied focus‐to‐detector distance of our fluoroscopic EPIDs. For low and high energy photon beams (6 and 23 MV) good agreement has been found between calculated and measured transmissions for a slab and a thorax phantom.
Electrodynamic headphones and woofers for application in magnetic resonance imaging scanners
Authors: Baumgart Frank , Kaulisch Thomas , Tempelmann Claus , Gaschler‐Markefski Birgit , Tegeler Carola , Schindler Frank , Stiller Detlef , Scheich Henning
Published: July 2002

Electrodynamic speakers compatible with (functional) magnetic resonance imaging (MRI) are described. The speakers magnets are removed, their function is replaced by the scanner's magnetic field, resulting in an uncommon but efficient operation. The method can be used with headphones as well as woofers. Functional MRI is not associated with any known biological risks, but as a method for visualization of task‐specific activation of brain regions it is undesirably noisy. Thus, it requires both noise protection and efficient sound transmission systems for delivering acoustic stimuli to subjects. Woofers could possibly be used in active noise‐control systems. The speakers described in this paper can be used for either task.
Experimental assessment of power and temperature penetration depth control with a dual frequency ultrasonic system
Authors: Moros Eduardo G. , Fan Xiaobing , Straube William L.
Published: July 2002

A novel ultrasound applicator for superficial simultaneous thermoradiotherapy consisting of two parallel‐opposed linear arrays and a double‐sided scanning reflector was constructed and tested for penetration depth control. In this design the arrays operate at different frequencies (1 and 5 MHz, in this study) and the input power to each array element (five elements per array) is computer adjustable. The ultrasonic beams from the arrays are aimed at the scanning reflector which in turn deflects them simultaneously and in parallel toward the treatment volume. Relative intensity distributions generated by the prototype were measured in a degassed water phantom using a thermal technique for a selected reflector position; these showed that the ultrasonic intensity distribution can be controlled in the lateral dimensions by varying the input power level to individual array elements. A fixed‐perfused canine kidney phantom was employed to demonstrate experimentally that real time penetration depth control is possible by varying the excitation magnitude of one array (frequency) relative to that of the other. It is concluded that the dual‐frequency scanned‐reflected ultrasound applicator offers a degree of dynamic three‐dimensional control of the power deposition pattern of clinical significance.
Ridge filter design and optimization for the broad‐beam three‐dimensional irradiation system for heavy‐ion radiotherapy
Authors: Schaffner Barbara , Kanai Tatsuaki , Futami Yasuyuki , Shimbo Munefumi , Urakabe Eriko
Published: July 2002

The broad‐beam three‐dimensional irradiation system under development at National Institute of Radiological Sciences (NIRS) requires a small ridge filter to spread the initially monoenergetic heavy‐ion beam to a small spread‐out Bragg peak (SOBP). A large SOBP covering the target volume is then achieved by a superposition of differently weighted and displaced small SOBPs. Two approaches were studied for the definition of a suitable ridge filter and experimental verifications were performed. Both approaches show a good agreement between the calculated and measured dose and lead to a good homogeneity of the biological dose in the target. However, the ridge filter design that produces a Gaussian‐shaped spectrum of the particle ranges was found to be more robust to small errors and uncertainties in the beam application. Furthermore, an optimization procedure for two fields was applied to compensate for the missing dose from the fragmentation tail for the case of a simple‐geometry target. The optimized biological dose distributions show that a very good homogeneity is achievable in the target.
Determination of melting temperature and heat of fusion of a solid using a computer-interfaced temperature probe
Authors: Jogad Mahantappa S. , Van Domelen David , Westfall Gary , Benenson Walter , Mahanti S. D.
Published: July 2002

This paper describes a relatively simple laboratory exercise enabling students to find the melting temperature of a solid with a low melting point, and to estimate its heat of fusion.
The art of statistical mechanics: Looking at microscopic spectra and seeing macroscopic phenomena
Authors: Prentis Jeffrey J. , Zainiev Timur
Published: July 2002

Simple graphical spectra are presented as visual paradigms for the basic ideas of statistical mechanics. Each spectrum is designed so that the mechanical information can be readily converted into thermal and statistical properties.
A reliable, compact, and low-cost Michelson wavemeter for laser wavelength measurement
Authors: Fox P. J. , Scholten R. E. , Walkiewicz M. R. , Drullinger R. E.
Published: July 2002

We describe the construction and operation of a simple, compact, and cost effective Michelson wavemeter with picometer accuracy. The low cost of the device means that it can form the basis of an undergraduate laboratory experiment, yet it is sufficiently reliable and accurate that it has become an important tool in our research laboratory, where it is regularly used to tune lasers to atomic transitions. The usefulness and accuracy of the wavemeter is demonstrated by tuning two separate extended cavity diode lasers to achieve two-step excitation of the Rb 52D state, observed by detecting 420 nm blue fluorescence from the 52D→62P→52S decay path.
Zones of impact around icebreakers affecting beluga whales in the Beaufort Sea
Authors: Erbe Christine , Farmer David M.
Published: July 2002

A software model estimating zones of impact on marine mammals around man-made noise [C. Erbe and D. M. Farmer, J. Acoust. Soc. Am. 108, 1327–1331 (2000)] is applied to the case of icebreakers affecting beluga whales in the Beaufort Sea. Two types of noise emitted by the Canadian Coast Guard icebreaker Henry Larsen are analyzed: bubbler system noise and propeller cavitation noise. Effects on beluga whales are modeled both in a deep-water environment and a near-shore environment. The model estimates that the Henry Larsen is audible to beluga whales over ranges of 35–78 km, depending on location. The zone of behavioral disturbance is only slightly smaller. Masking of beluga communication signals is predicted within 14–71-km range. Temporary hearing damage can occur if a beluga stays within 1–4 km of the Henry Larsen for at least 20 min. Bubbler noise impacts over the short ranges quoted; propeller cavitation noise accounts for all the long-range effects. Serious problems can arise in heavily industrialized areas where animals are exposed to ongoing noise and where anthropogenic noise from a variety of sources adds up.
Active noise control in a free field with virtual sensors
Authors: Kestell Colin D. , Cazzolato Ben S. , Hansen Colin H.
Published: July 2002

The zone of local control around a “virtual energy density sensor” is compared with that offered by an actual energy density sensor, a single microphone, and a virtual microphone. Intended as an introduction to the concept of forward difference prediction and a precursor to evaluating the virtual sensor control algorithms in damped enclosures, this paper investigates an idealized scenario of a single primary sound source in a free-field environment. An analytical model is used to predict the performance of the virtual error sensors and compare their control performance with their physical counterparts. The model is then experimentally validated. The model shows that in general the virtual energy density sensor outperforms the actual energy density sensor, the actual microphone, and the virtual microphone in terms of centering a practically sized zone of local control around an observer who is remotely located from any physical sensors. However, in practice, the virtual sensor algorithms are shown to be sensitive (by varying degrees) to short wavelength spatial pressure variations of the primary and secondary sound fields.
Modeling of bottom backscattering from three-dimensional volume inhomogeneities and comparisons with experimental data
Authors: Li Dan , Frisk George V. , Tang Dajun
Published: July 2002

In this paper, backscattering from 3D volume inhomogeneities in the seabed is modeled and the results compared with experimental data at 250–650 Hz. The experiment was part of the Acoustic Reverberation Special Research Program (ARSRP) and the data were obtained in a sediment pond on the western flank of the Mid-Atlantic Ridge. A volume scattering model based on first-order perturbation theory is developed incorporating contributions from both sound speed and density fluctuations. With the propagators, i.e., the Green’s functions, handled accurately through numerical wave number integration and random fluctuations generated effectively by a new scheme modified from the spectral method, the model is capable of simulating monostatic, backscattered fields in the frequency domain as well as in the time domain owing to 3D volumetric sediment inhomogeneities. The model compares favorably and consistently with the ARSRP backscattering data over the entire frequency band, with the fluctuations of sound speed and density in two irregular sediment layers, identified from the data analysis, described by a power-law type of power spectrum.
The effects of compression ratio, signal-to-noise ratio, and level on speech recognition in normal-hearing listeners
Authors: Hornsby Benjamin W. Y. , Ricketts Todd A.
Published: July 2002

Previous research has demonstrated reduced speech recognition when speech is presented at higher-than-normal levels (e.g., above conversational speech levels), particularly in the presence of speech-shaped background noise. Persons with hearing loss frequently listen to speech-in-noise at these levels through hearing aids, which incorporate multiple-channel, wide dynamic range compression. This study examined the interactive effects of signal-to-noise ratio (SNR), speech presentation level, and compression ratio on consonant recognition in noise. Nine subjects with normal hearing identified CV and VC nonsense syllables in a speech-shaped noise at two SNRs (0 and +6 dB), three presentation levels (65, 80, and 95 dB SPL) and four compression ratios (1:1, 2:1, 4:1, and 6:1). Stimuli were processed through a simulated three-channel, fast-acting, wide dynamic range compression hearing aid. Consonant recognition performance decreased as compression ratio increased and presentation level increased. Interaction effects were noted between SNR and compression ratio, as well as between presentation level and compression ratio. Performance decrements due to increases in compression ratio were larger at the better (+6 dB) SNR and at the lowest (65 dB SPL) presentation level. At higher levels (95 dB SPL), such as those experienced by persons with hearing loss, increasing compression ratio did not significantly affect speech intelligibility.
Linear and nonlinear frequency shifts in acoustical resonators with varying cross sections
Authors: Hamilton Mark F. , Ilinskii Yurii A. , Zabolotskaya Evgenia A.
Published: July 2002

The frequency response of a nonlinear acoustical resonator is investigated analytically and numerically. The cross-sectional area is assumed to vary slowly but otherwise arbitrarily along the axis of the resonator, such that the Webster horn equation provides a reasonable one-dimensional model in the linear approximation. First, perturbation theory is used to derive an asymptotic formula for the natural frequencies as a function of resonator shape. The solution shows that each natural frequency can be shifted independently via appropriate spatial modulation of the resonator wall. Numerical calculations for resonators of different shapes establish the limits of the asymptotic formula. Second, the nonlinear interactions of modes in the resonator are investigated with Lagrangian mechanics. An analytical result is obtained for the amplitude-frequency response curve and nonlinear resonance frequency shift for the fundamental mode. For a resonator driven at its lowest natural frequency, it is found that whether hardening or softening behavior occurs depends primarily on whether the nonlinearly generated second-harmonic frequency is greater or less than the second natural frequency of the resonator. A fully nonlinear one-dimensional numerical code is used to verify the analytical result.
Formant-frequency matching between sounds with different bandwidths and on different fundamental frequencies
Authors: Dissard Pascal , Darwin C. J.
Published: July 2002

The two experiments described here use a formant-matching task to investigate what abstract representations of sound are available to listeners. The first experiment examines how veridically and reliably listeners can adjust the formant frequency of a single-formant sound to match the timbre of a target single-formant sound that has a different bandwidth and either the same or a different fundamental frequency (F0). Comparison with previous results [Dissard and Darwin, J. Acoust. Soc. Am. 106, 960–969 (2000)] shows that (i) for sounds on the same F0, introducing a difference in bandwidth increases the variability of matches regardless of whether the harmonics close to the formant are resolved or unresolved; (ii) for sounds on different F0’s, introducing a difference in bandwidth only increases variability for sounds that have unresolved harmonics close to the formant. The second experiment shows that match variability for sounds differing in F0, but with the same bandwidth and with resolved harmonics near the formant peak, is not influenced by the harmonic spacing or by the alignment of harmonics with the formant peak. Overall, these results indicate that match variability increases when the match cannot be made on the basis of the excitation pattern, but match variability does not appear to depend on whether ideal matching performance requires simply interpolation of a spectral envelope or also the extraction of the envelope’s peak frequency.
Acoustic chaos in a duct with two separate sound sources
Authors: Dong W. G. , Huang X. Y. , Wu Q. L.
Published: July 2002

Nonlinear interaction of two plane acoustic waves in the (0,0) mode of a square duct is investigated from the viewpoint of chaotic dynamics. Phase-space portraits are reconstructed from time series obtained in an experiment. It is demonstrated that limit sets formed by the phase space trajectories are “attractors.” The largest Lyapunov exponent and correlation dimension of these attractors are calculated, and the results indicate that these attractors are chaotic.
Lagrangian effective material constants for the modeling of thermal behavior of acoustic waves in piezoelectric crystals. II. Applications and numerical values for quartz
Authors: Dulmet B. , Bourquin R. , Bigler E. , Ballandras S.
Published: July 2002

This paper presents a set of numerical values of temperature derivatives of Lagrangian effective elastic coefficients suitable for the modeling of small vibrations in quartz devices submitted to slow and homogeneous temperature variations. After a short description of the proper writing of vibration problems in practical applications with the help of this kind of coefficient, we determine the proposed set of numerical values from the frequency–temperature characteristics of an heterogeneous set of bulk and surface acoustic wave devices.
An approximation to the far field and directivity of elastic wave transducers
Authors: Bakker Maarten C. M. , Verweij Martin D.
Published: July 2002

The far field of surface mounted elastic wave transducers, as used in Non-Destructive Testing (NDT), is analyzed in order to understand the mechanisms that determine the directivity of these devices. To model the physical configuration, a moving distribution of normal traction, acting at the free surface of an elastic half-space, is used. The exact field expression consists of a spatial superposition of the elementary waves emitted by the hypothetical point sources that make up the finite source. The current aim is to derive approximate far field expressions that are physically instructive and numerically fast. This is achieved through a paraxial approximation of the elementary waves and a Taylor approximation of their arrival times. The approximate expressions thus obtained, consist of a time convolution of a paraxial wave and a transfer function. The latter represents the influence of the source geometry. Besides elucidating the mechanisms of directivity, the analysis renders a rule of thumb for synthesizing a source with a desired directivity pattern. Numerical experiments show that the approximations reduce the computational effort by a factor of 1000, and that the accuracy of the approximate far field and directivity proves excellent at distances beyond a few times the characteristic source size.
Application of narrow band laser ultrasonics to the nondestructive evaluation of thin bonding layers
Authors: Liu Y.-H. , Wu T.-T. , Lee C.-K.
Published: July 2002

In this paper, a modified laser induced grating technique (LIG) has been utilized to generate narrow band surface waves in an epoxy-bonded copper-aluminum layered structure. A high performance optical interferometer system was utilized to detect the laser-generated surface waves. The dispersion of surface wave in an epoxy-bonded copper-aluminum specimen was measured and compared with the theoretical solution. An inverse algorithm based on the simplex method was then introduced to determine the bonding thickness as well as the elastic properties of the bonding layer. The inversion results demonstrated that the thickness in the μm range or the elastic properties of the bonding layer could be successfully determined.
A passive nonlinear digital filter design which facilitates physics-based sound synthesis of highly nonlinear musical instruments
Authors: Pierce John R. , Van Duyne Scott A.
Published: July 2002

Recent work has led to highly efficient physics-based computational models of wave propagation in strings, acoustic tubes, membranes, plates, and rooms using the digital waveguide filter, the 2-D digital waveguide mesh, and the 3-D tetrahedral digital waveguide mesh, all of which are suitable for real-time musical synthesis applications. A simple first-order nonlinear filter structure derived from a passive nonlinear impedance circuit is described which extends the usefulness of these models, and which avoids the difficulties of energy conservation when memoryless nonlinearities are inserted in resonant feedback systems.
Improving discrimination of confusable words using the divergence measure
Authors: Loizou Philipos , Spanias Andreas
Published: July 2002

This paper describes the use of the divergence measure as a criterion for finding a transformation matrix which will map the original speech observations onto a subspace with more discriminative ability than the original. A gradient-based algorithm is also proposed to compute the transformation matrix efficiently. The subspace approach is used as a preprocessing step in a hidden Markov model (HMM) based system to enhance discrimination of acoustically similar pairs of words. This approach is compared with standard linear discriminant analysis (LDA) techniques and shown to yield as much as 4.5% improvement. The subspace approach is also applied successfully to a more general recognition problem, i.e., discrimination of K confusable words, using the average divergence measure.
A change of subscripts of the stimulus placements for a four-point sampling method
Authors: Lam Chan F. , Mills John H. , Dubno Judy R.
Published: July 2002

Because the variance parameter, σ, in a cumulative normal function is not the same as the spread parameter, S, of a logistic function, the subscripts of the four stimulus placements of Eq. (3), and thereafter, of Lam et al. [J. Acoust. Soc. Am. 99, 3689–3693 (1996)] should be X12, X27, X73, and X88.
Relations between notched-noise suppressed TEOAE and the psychoacoustical critical bandwidth
Authors: Neumann Joachim , Uppenkamp Stefan , Kollmeier Birger
Published: July 2002

Narrow-band transitory evoked otoacoustic emissions (TEOAE) were recorded for nine normal hearing subjects in the presence of a broadband tone complex suppressor. Introducing a spectral notch at the frequency of the narrow-band stimulus causes the suppression effect to decrease, the more so the wider the notch. This decrease in suppression permits an estimate of the size of one critical band. One advantage of this approach is that no active participation of the subjects is required. The estimated critical bandwidth is then compared with independent estimates based on a simultaneous masking experiment, using the same stimuli. The two measures of the critical bandwidth coincide well for those six subjects with spontaneous otoacoustic emissions. However, the bandwidth estimate based on the OAE measurements is too large for the other three subjects without spontaneous emissions. Simulations of the suppression effect with a driven van der Pol oscillator with moderate undamping produce critical bandwidth estimates consistent with those observed in the psychoacoustical experiments. This allows an estimate of the “effective” amount of undamping on the basilar membrane that is required to produce the critical bandwidth observable in psychoacoustic experiments.
Sensitivity of the cochlear nucleus octopus cell to synaptic and membrane properties: A modeling study
Authors: Kipke Daryl R. , Levy Kenneth L.
Published: July 2002

Octopus cells of the posteroventral cochlear nucleus precisely fire at the onset of short-duration tone bursts, followed by little sustained activity. While this characteristic onset response has been described in experimental studies, its underlying mechanisms are not completely known. The objective of this study was to investigate these mechanisms through a sensitivity analysis of selected parameters of a compartmental model of the octopus cell. The parameters relate to cell morphology, passive electrical properties, synaptic inputs, and active channels. The modeled responses were used to evaluate the effects of four postulated mechanisms on the onset response: the cell’s small membrane time constant, the cell’s numerous weakly effective excitatory inputs, increases in spike threshold caused by sustained depolarization, and electrical loading of the soma by the dendrites. Simulations indicate that the model’s onset response to tone bursts is an emergent property of multiple cell parameters that is best predicted by the ratio of synaptic conductance density to membrane leakage conductance density and by the level of sustained depolarization during the tone burst.
Active structural acoustic control using strain sensing
Authors: Masson P. , Berry A. , Nicolas J.
Published: July 2002

A new strategy based on the direct use of strain sensing is proposed for the minimization of the acoustic radiation from a vibrating plate. This strategy uses active structural acoustic control because it eliminates the need for far-field acoustic sensors. The cost function is defined as the radiated acoustic power and the discrete strain information is given directly, for example, by fiber optic sensors embedded in the structure. Two approaches are presented to express the cost function in terms of strain information. The first one is based on plate’s displacement reconstruction from the strain field while the second is based on integration by parts of the wave-number transform of the displacement. Proper concentration of the control effort is obtained with the cost function defined in the wave-number domain. Both approaches are first validated with respect to an analytical solution for the calculation of the radiated acoustic power from structural strain information. It is shown that good agreement is obtained with at least two strain sensors per structural wavelength. Optimal control of acoustic radiation from a simply supported plate is then performed using different configurations of sensors and actuators. The control is performed using simulated piezoelectric actuators and results show that both approaches are well suited for active control applications as they offer good performance over a wide frequency range while requiring only few sensors.
Measurements and analysis of acoustic backscattering by elastic cubes and irregular polyhedra
Authors: Thorne Peter D. , Sun Shaobo , Zhang Jingdong , Bjorno Irina , Mazoyer Thierry
Published: July 2002

Underwater acoustic studies of backscattering by submerged targets have generally focused on bodies with spherical and cylindrical symmetry. However, there are interests in scattering by objects which may be characterized by more angular features, with surfaces that tend to be composed of facets and edges. To investigate the scattering properties of such bodies, the backscattering by a number of elastic cubes, and irregularly shaped polyhedra, have been studied. Data were collected by measuring the band limited impulse response of the scatterers, using a broadband transducer, which operated as a transceiver, both transmitting and receiving signals. To present the scattering measurements nondimensionally a form function definition has been employed to normalize the backscattered signals. The normalized frequency has been expressed as ka, where k is the acoustic wave number, and a is a characteristic dimension of the scatterer. The cube observations covered a broad ka range, ka=3–34, thereby encompassing the lower ka scattering region where the cube can be considered to be nominally rigid, through to higher ka values where it would be expected that the elastic properties of the cube become important. The measurements on irregular polyhedra are more limited in extent, however, the results are presented for comparison with the cube data. To compare the observations with predictions, computations of acoustic backscattering for both rigid and elastic cubes are presented.
Further investigation on actively created quiet zones by multiple control sources in free space
Authors: Guo Jingnan , Pan Jie
Published: July 2002

Further research on the quiet zones created in the free space, using multiple control sources and error microphones located in two parallel planes, indicated that there also exists a range of optimal spacing for the control sources and error microphones. Both the computer simulations and experimental results show that the control system can create the largest quiet zone and suffer the least increase of total sound power output when the control actuators and sensors are arranged within this optimal range.
A three-dimensional finite difference code for the modeling of sonic logging tools
Authors: Chen Yong-Hua , Chew Weng Cho , Liu Qing-Huo
Published: July 2002

This paper presents a numerical program for the simulation of elastic wave propagation and scattering in three-dimensional (3-D) cylindrical coordinates based on the first-order velocity-stress finite-difference scheme on staggered grids. Both Liao’s and Lindman’s absorbing boundary conditions are implemented for the exterior boundaries to efficiently truncate the computation domain for elongated 3-D well logging problems. Symmetric and anti-symmetric boundaries in azimuthal and axial directions are also implemented in the code to further reduce the size of the problem. Included for the first time with this code are very large and complex geometrical structures such as the whole slotted sleeve housing of a sonic well-logging tool which typically involves hundreds of millions of unknowns. The calculation for such a large problem only takes a couple of days on a four-processor SGI Power Challenge machine. Different types of slotted sleeve models are studied for sonic logging tools. Simulation results show that different slotted sleeves vary widely in delaying and attenuating the pipe waves which travel along the tool housing. A new slotted sleeve structure with three horizontal slot sections for every vertical slot period is proposed for better performance. A dipole source is found to produce much cleaner waveforms than a monopole source.
Comparison of speech intelligibility between English and Chinese
Authors: Kang Jian
Published: July 2002

Most objective indices for speech intelligibility are essentially based on studies of Western languages and not tonal languages like Chinese. Consequently, if speech intelligibility in an enclosure is satisfactory for English, it is not necessarily satisfactory for Chinese, or vice versa. In this research, the differences in intelligibility between English and Mandarin (a spoken language of Chinese) have been investigated by carrying out a series of articulation tests in a long corridor and a regularly shaped (i.e., quasi-cubic) seminar room, using loudspeaker sources. The results suggest that in terms of speech intelligibility, Mandarin is slightly better than English under reverberant conditions, and English is considerably better than Mandarin under noisy conditions.
Fluid column resonances of water-filled cylindrical shells of elliptical cross section
Authors: Chinnery Paul A. , Humphrey Victor F.
Published: July 2002

The acoustic resonances of a submerged fluid-filled cylindrical shell are analyzed as the shell cross section is deformed from circular to elliptical geometry. A schlieren visualization system is used to image standing wave fields within insonified water-filled shells of different eccentricities, and to locate the resonance frequencies of the fluid column. The acoustic behavior of elliptical cavities with infinite and finite surface impedances are modeled and the theory used to predict the resonance frequencies of the fluid column and calculate the pressure distribution in the acoustic field. As the symmetry of the circular shell is broken by deforming it to the more general ellipse the resonance spectrum changes; mode splittings and level crossings are observed as the eccentricity increases. The experimental observations of resonance patterns and frequency variation are in good agreement with the theoretical predictions.
An alternative formulation for predicting sound radiation from a vibrating object
Authors: Wu Sean F. , Hu Qiang
Published: July 2002

An alternative formulation is derived for predicting acoustic radiation from a vibrating object in an unbounded fluid medium. The radiated acoustic pressure is shown to be expressible as a surface integral of the particle velocity, which is determinable by using a nonintrusive laser velocimeter. This approach is in contrast with the Kirchhoff integral formulation which requires the knowledge of both the normal component of the surface velocity and the surface acoustic pressure prior to predicting the radiated acoustic pressure. Solutions thus obtained are unique. Moreover, the efficiency of numerical computations is high because the surface integration can be readily implemented numerically by using standard Gaussian quadratures. This alternative formulation may be desirable to analyze the acoustic and vibration responses of a lightweight, a flexible, or a structure under an adverse environment for which a nonintrusive laser measurement technique must be used. Validations of this alternative formulation are demonstrated both analytically and numerically for vibrating spheres and right circular cylinders.
A conceptual experiment of direct converting digital microphone
Authors: Yasuno Yoshinobu , Riko Yasuhiro
Published: July 2002

A transducer which directly converts signals from analog acoustic to digital electric is described. This consists of a subtracter, a sampling and holding circuit, a sigma-delta modulation circuit as a comparator, an accumulator, and a local digital-to-analog converter similar to a typical electric analog-to-digital converter. The subtracter is an electrostatic device which has a diaphragm, driving electrode, and detecting electrode. The driving electrode is divided into corresponding digital signal bits by the ratio of each area which enables one to drive the diaphragm digitally and is regarded as an electroacoustic digital-to-analog converter. The detecting electrode makes electric signals proportional to the displacement of the diaphragm driven by subtracting the incoming acoustic signal and electrically driven force. This is regarded as the subtracter. This detected signal is amplified and sampled-held and modulated by the sigma-delta procedure and generates subtracted signal to + or −1 bit which is added to the accumulator memory by a very high-speed clock rate. The output of the accumulator is the digital signal output and is also given to the driving electrodes. A 4-bit conceptual device was developed for an experiment. Some results will be reported.
Three-dimensional propagation effects: Modeling, observations, and suggested benchmark cases
Authors: Smith Kevin B.
Published: July 2002

Over the past several years, many acoustic propagation models have been adapted to compute the influence of azimuthal coupling. These so-called three-dimensional (3-D) models should provide more accurate predictions of the acoustic field in 3-D variable environments than previous 2-D×N models. However, such advanced 3-D propagation models are generally slower than their 2-D×N predecessors. It is, therefore, important to understand the significance of the difference between 3-D and 2-D×N and when such effects should be considered. Furthermore, as of this date, no formal set of benchmark cases and solutions has been defined to test the accuracy of the various 3-D models currently being used. This paper will provide a general overview of 3-D propagation models and how they can be used to assess the significance of azimuthal coupling in ocean acoustics. Specific examples of such influences will be provided from a 3-D parabolic equation model and compared to results from the corresponding 2-D×N version. Of particular interest will be the pseudo-3-D effects predicted by 2-D×N calculations and the ability to distinguish true 3-D effects in experimental data. Finally, several environmental scenarios will be suggested as possible benchmark cases for future studies. [Work sponsored by ONR Code 321OA.]
Fuzzier but simpler analytic models for physical acoustics and structural acoustics
Authors: Pierce Allan D.
Published: July 2002

Acousticians have long been forced to analyze physical systems for which they apparently do not have enough information to make detailed analytical or computational predictions. One could say that their knowledge of such systems is ‘‘fuzzy.’’ Alternately, the means of measuring the details or of describing such a system may be in principle possible, but the answers one really desires, those which one can ‘‘deal with,’’ are of seemingly far less complexity than the modeled system in all its detail. The trick, of course, is to hypothesize a small number of simple and relevant descriptors of the system and to build a predictive model that uses only these descriptors. The rich and venerable literature of acoustics abounds with successful attempts in this vein, and a few such, taken from diverse subfields such as physical acoustics, architectural acoustics, underwater acoustics, and structural acoustics, are briefly reviewed in this talk. New problems and new questions lead to new searches for appropriate descriptors and for simple models which employ these descriptors. Theoretical tools which help to fill in the gaps caused by the incompleteness of these descriptors are general conservation principles and Jayne’s theory of maximum-likelihood based on Shannon’s uncertainty function.
Inversion of source-time functions using borehole array sonic waveforms
Authors: Chang Chung , Liu Qing-Huo
Published: July 2002

Many geophysical applications of the array sonic measurements require the knowledge of the true source-time function. Recovery of the source-time function from the borehole sonic P head waves is different from the source inversion problem in exploration seismology. The difficulty in the inversion of borehole sonic measurements arises due to the inexact knowledge of the impulse response, e.g., the inability to model the whole problem including the tool body and transducers. The random noise often encountered in seismic signals is not the key obstacle here. The inverse source problem is ill posed due to the interference of P head-wave multiples. Using waveforms from a laboratory scale model we have applied two deconvolution methods, one using a Wiener filter and the other the time-domain least-squares method. As expected, without constraints on the solutions, one cannot recover a satisfactory source-time function. An unconventional smoothness constraint is applied in the source spectrum (instead of the usual smoothness in the time-domain signals), which corresponds to a finite-duration pulse in the time domain (instead of the usual band-limited spectrum). This technique is thus called the “duration-limited” inversion. The inverted results, obtained by Wiener filtering combined with this “duration limiting” process and multichannel stacking, agree well with an independent free-field measurement. Furthermore, reconstructed receiver waveforms using the inverted source function match the measured ones. The inversion procedure is robust and potentially useful for field measurements.
The solution for the propagation of sound in a toroidal waveguide with driven walls (the acoustitron)
Authors: Lawrenson Christopher C. , Lafleur L. Dwynn , Shields F. Douglas
Published: July 2002

This paper describes the theory of sound propagation in a toroidal waveguide with driven walls. This configuration has the advantage of simulating a tube of infinite length. The general solution for the velocity potential is derived in terms of an arbitrary function which represents the angular dependence of the disturbance of the driving wall. Two different cases are considered. The first is a toroid with the wall driven at a single angular position. The second case is a toroid with walls driven such that a traveling wave is generated in the wall with a controllable wave number and frequency. A traveling wave is produced inside the toroid when the circumference of the toroid is a whole number of wavelengths for the wave in the wall. The amplitude of the traveling wave is a function of the intrinsic speed of sound in the medium inside the toroid. A device we call an acoustitron was constructed to verify the results of the latter case. Experimental results agree well with those predicted by theory.
High-frequency audibility: Benefits for hearing-impaired listeners
Authors: Hogan Cynthia A. , Turner Christopher W.
Published: July 2002

The present study was a systematic investigation of the benefit of providing hearing-impaired listeners with audible high-frequency speech information. Five normal-hearing and nine high-frequency hearing-impaired listeners identified nonsense syllables that were low-pass filtered at a number of cutoff frequencies. As a means of quantifying audibility for each condition, Articulation Index (AI) was calculated for each condition for each listener. Most hearing-impaired listeners demonstrated an improvement in speech recognition as additional audible high-frequency information was provided. In some cases for more severely impaired listeners, increasing the audibility of high-frequency speech information resulted in no further improvement in speech recognition, or even decreases in speech recognition. A new measure of how well hearing-impaired listeners used information within specific frequency bands called “efficiency” was devised. This measure compared the benefit of providing a given increase in speech audibility to a hearing-impaired listener to the benefit observed in normal-hearing listeners for the same increase in speech audibility. Efficiencies were calculated using the old AI method and the new AI method (which takes into account the effects of high speech presentation levels). There was a clear pattern in the results suggesting that as the degree of hearing loss at a given frequency increased beyond 55 dB HL, the efficacy of providing additional audibility to that frequency region was diminished, especially when this degree of hearing loss was present at frequencies of 4000 Hz and above. A comparison of analyses from the “old” and “new” AI procedures suggests that some, but not all, of the deficiencies of speech recognition in these listeners was due to high presentation levels.
Transducer misalignment effects in beam reflection from elastic structures
Authors: Zhang Han , Chimenti D. E. , Zeroug Smaine
Published: July 2002

In two-transducer, fluid-coupled ultrasonic reflection measurements phase matched to guided modes of elastic solid structures, the effects of misalignment (i.e., differences) between the receiver angle and the incident beam angle on the receiver voltage have been studied. The received voltage is typically due to contributions from the specular reflection and any of the several possible guided wave modes excited by the incident wave field. It is found that misalignment leads to changes in the relative amplitudes of the various contributions. Further, the more highly collimated the beam (or the contributor), the more pronounced are the effects. It is shown that the signal maximum is not a reliable indicator of receiver alignment. These conclusions are based on measurements and on calculations that have been performed at incident angles selected both close to, or far from, phase-matching angles to guided wave modes on plates, curved surfaces, and cylindrical shells. Receiver voltage coordinate scans have been performed with receiver angles misaligned from the incident beam axis by 1 to 4 degrees. The receiver voltage versus scan parameter in planar and curved structures is calculated by employing complex transducer points to synthesize two-dimensional, sheet-beam transducer fields with Gaussian apertures, spectral analysis to formulate the beam-structure interaction problem, and asymptotic methods to evaluate the resulting spectral integrals. The model predictions are generally in good agreement with the experiments.
Noise control of a master harmonic oscillator coupled to a set of satellite harmonic oscillators
Authors: Maidanik G. , Becker K. J.
Published: July 2002

The overall gain is defined as the ratio of the stored energy in the isolated master harmonic oscillator to that in the coupled one. This gain is composed of two distinct factors: The first factor, the external input power gain, relates to the ratio of the external input power into the isolated master harmonic oscillator to that into the coupled one. The second factor, the loss factor gain, relates to the ratio of the loss factor of the coupled master harmonic oscillator to that of the isolated master harmonic oscillator. Both loss factors are in reference to the stored energy in the master harmonic oscillator only. It has been customary to assume the first factor to be unity and, thus the overall gain and the loss factor gain have been assumed to be identical. It is argued here that often this assumption is not valid. Therefore, noise control measures that are based on this assumption may have been wrongly evaluated. A few examples that illustrate the disparity between the overall gain and the loss factor gain are cited in this paper.
Reed vibration and sound generation in lingual organ pipes
Authors: Rossing Thomas D. , Angster Judit , Miklós András
Published: July 2002

The reed velocity and the sound pressure inside the shallot have been recorded in lingual organ pipes as the vibrating reed length is varied by means of the tuning wire (Stimmkrücke) (in an F3 trompette pipe, for example, the sounding frequency was varied from 157 to 325 Hz). Without the resonator, the frequency is a continuous function of the reed vibrating length, but when the conical resonator is added, the pipe frequency jumps abruptly from below to above each resonance frequency of the sonator. When the natural frequency of the reed (excited by plucking) was varied from 138 to 316 Hz by changing its vibrating length, the pipe frequency changed from 170 to 340 Hz. Reed closure may induce a strong acoustical oscillation in the shallot at a high frequency (approximately 1700 Hz in the F3 trompette pipe) which strengthens a certain range of harmonics and gives rise to a formant in the pipe sound. The oscillation frequency in the shallot rises rapidly as the reed closes it, and reaches a frequency near the resonance frequency of a tube of comparable length with one closed end. When the resonator is attached, the shallot oscillations are strongly damped. a)Permanent address: Physics Dept., Northern Illinois University, DeKalb, IL 60115.