bluuebunny/crossref_metadata_2025 huggingface dataset:
Word recognition by humans and machines: Tests on a multitalker, multistyle database
Authors: Kuhl Patricia K. , Green Kerry P. , Gordon John W. , Sanford David L. , Fu Caroline
Published: October 2005

Experiments comparing isolated word recognition by human listners with automatic speech recognition systems are valuable because error analyses may lead to improvements in speech recognition technology. Isolated word recognition in adult human listeners has been compared with recognition performance by two commercially available speech-recognition systems. The test stimuli were drawn from the Lincoln Laboratory Stressed-Speech database. The database consists of 6930 stimuli (two iterations of each of 35 words spoken by nine different people in 11 different speaking styles). The vocabulary contains confusable words (i.e., go, hello, oh, no, and zero); the speaking styles include a wide range of naturally occurring variations (i.e., normal, slow, fast, soft, loud, angry). Analyses show that the acoustic characteristics of individual words vary considerably across talkers, and across styles within talkers. Performance of human listeners and the two machine-based recognition systems was tested in a single-talker, multistyle condition, and in a multitalker, multistyle condition. All tests were conducted under two listening conditions: normal, and in the presence of masking noise. The data to be presented are the error patterns of human listeners, versus the machine-recognition systems, exhibited across talkers, across speaking styles, and across training conditions (multitalker, multistyle training versus single talker, single style training). [Work supported by Boeing Aerospace and Electronics.]
Transitional cues and redundancy in speech recognition
Authors: Scott Brian L. , Smith Lloyd A. , Lin Lisan S. , Newell J. Mark
Published: October 2005

Perhaps the most difficult features for speech recognition systems to properly capture and align are the transitional cues that exist between phones. There are advantages and disadvantages associated with both linear time normalization methods and dynamic time warping (DTW). Linear methods preserve the relative durations of transitional and steady-state portions of the signal but tend to smear features and lose resolution. DTW retains resolution but loses durational relations. The present algorithm attempts to compensate for the smearing associated with linear normalization by copying transitional regions of the utterance to additional locations within the representation. This process involves locating the onset and offset of the syllable nucleus based on the normalized representation and copying two frames immediately surrounding the onset and offset to another location in the representation. The process enhances performance of the recognizer in two ways. First of all, the redundancy serves to weight more heavily the perceptually important transitional region that exists between consonantal cues, such as burst frequencies, frication, nasal murmurs, etc., and the vowel nucleus of the syllable. And second, copying these regions to another location within the representation serves to enhance the alignment of these cues during training and matching. The system is being evaluated over standard telephone lines using the alphabet as the test vocabulary. The telephone environment, and the inherent confusibility of the alphabet as a test vocabulary, places significant demands on the recognizer to accurately capture and identify transitional cues. The pilot study, using only a single speaker, provided encouraging results. The recognizer was 96.7% accurate over 8320 live trials. Currently, an alphabet database is being collected and speaker-independent test results will be presented.
Excitation waveform extraction for pitch control in residual-excited LPC speech synthesis
Authors: Itoh K. , Sato H.
Published: October 2005

The residual-excited LPC is one of the most effective techniques for producing high-quality synthetic speech. However, this technique has difficulty controlling pitch frequency when applied to realizing synthesized speech with a pitch contour different from original speech or when applied to synthesis of arbitrary speech created with concatenated spoken units. In previous methods, pitch-period LPC residual waveforms that extracted pitch synchronously have been used to control pitch frequency. However, the extraction position (Eρ) and window length (Ew) are very critical to synthesized speech quality, and cause voice quality deterioration. This paper proposes a new method of excitation waveform extraction that automatically determines Eρ and Ew using spectral envelope distortion criteria between input and synthetic speech. Subjective evaluation experiments indicate that the pitch frequency pattern can be changed with a relatively small deterioration in quality. Application of this method to arbitrary speech synthesis will also be discussed.
On the unit set design for speech synthesis by rule using nonuniform units
Authors: Sagisaka Yoshinori
Published: October 2005

The unit set design algorithm is proposed for nonuniform synthesis units using entropy measure. This algorithm enables optimal unit set building according to statistic phonotactic characteristics without using a priori linguistic knowledge. By considering each phoneme sequence unit as a state in nonuniform order Markov process, the entropy of a unit set is defined by the entropy of a Markov information source. Each unit candidate corresponds to a new state and the new state generation corresponds to the enrollment of the candidate as a unit member. Unit enrollment takes place by finding the corresponding new state that gives the greatest decrease to the entropy of the set. Applying this algorithm to Japanese using phoneme sequence statistics derived from a Japanese word dictionary, the following characteristics were observed. (1) Linguistically well-known CV-type syllables and diphthongs are selected in the very early stage. (2) Though the frequently used dyadic VC-type units are not selected in the early stage, the CVCV-type units that contain those VC-type units are selected in the earlier stages. (3) Many early selected units coincide with the phoneme sequence contained in morphemes. Through this experiment, it has turned out that the nonuniform unit set covered phoneme sequences about two times more efficiently than the usual uniform unit set.
Low-frequency acoustic tomography using matched field processing. II
Authors: Tolstoy A.
Published: October 2005

Part I discussed the difficulties and successes of the MFP technique in a range-independent environment. Part II discusses progress to data (simulations only) concerning a range-dependent eddy environment. First, a sound-speed structure is computed as the sum of two Gaussian eddys. Next sample sound-speed profiles are computed along a selected radial and used to calculate the basic EOFs for the entire environment. The EOFs themselves are fairly insensitive to how the sampling is done although their coefficients can change significantly. Given a set of EOFs, plots of their coefficients as a function of range and cross range show well-defined, easily interpolated behavior. Moreover, only two EOFs are needed to describe a sound-speed profile to a high degree of accuracy. Results will be presented examining the sensitivity of MFP to changes in the coefficients. Regions of high sensitivity require frequent profile estimations and increased environmental sampling. Progress to date suggests that the large family of parameter values (at least two parameters, i.e., EOF coefficients, per profile) plus iterative difficulties as seen in Part I may require the application of computationally intensive techniques such as simulated annealing.
Results in children using the 22-electrode cochlear implant
Authors: Dawson P. W. , Blamey P. J. , Clark G. M. , Busby P. A. , Rowland L. C. , Dettman S. J. , Brown A. M. , Dowell R. C. , Rickards F. W. , Alcantara J. I.
Published: October 2005

The Cochlear Implant Clinic, The Royal Victorian Eye and Ear Hospital, 32 Gisborne Street, East Melbourne, Victoria 3052, Australia Five children (aged 6.0 to 14.8 years) out of a group of nine implanted with the 22-electrode cochlear implant (Cochlear Pty. Ltd.) have achieved substantial open-set speech recognition scores for monosyllabic word (30% to 72% for phonemes) and sentence (26% to 74% for words in sentences) tests using hearing without lipreading. Four of these five children were implanted during preadolescence and the fifth, who had a progressive loss, was implanted during adolescence. The remaining children who did not demonstrate open-set recognition were implanted during adolescence after a long duration of profound deafness. Post-operative performance on closed-set speech perception tests was better than preoperative performance for the group of five children with open-set recognition. Improvements in speech and language assessments were also noted for these children. The results are discussed with reference to variables that may contribute to successful implant use, such as age of onset of loss, duration of profound loss, age at implantation, aetiology, educational program, and the type of training provided.
Speech feature recognition by profoundly deaf children using the University of Melbourne multichannel electrotactile aid
Authors: Alcantara Joseph I. , Whitford L. A. , Blamey P. J. , Cowan R. S. C. , Clark G. M.
Published: October 2005

Seven prelinguistically profoundly deaf children between 7 and 11 years of age were trained in the perception of vowel duration and place, the fricative /s/, and manner of articulation (/m/vs/b/, and /s/vs/t/) distinctions in the tactile-plus-hearing (TA} and tactile (T) conditions. Speech feature recognition tests were conducted in the TA, T, and hearing (A) conditions during the following: pre-training, during-training, and post-training phases. Test scores in the TA and T conditions were significantly greater than A condition scores for all but one test, suggesting that the addition of the tactile supplement improved the perception of these features. During- and post-training phase test scores in the TA and T conditions were significantly greater than pre-training scores suggesting that the training given was responsible for the improvement in feature perception. During- and post-training scores were similar suggesting that perceptual skills acquired during training were retained after training had been removed.
Loudness summation study on multielectrode pair stimulation
Authors: Lim H. H. , Tong Y. C. , Hollow R. D. , Vandali A. E. , Hoesel R. V.
Published: October 2005

This psychophysical study investigated loudness summation for the activation of two, three, or four electrode pairs in a stimulus period. The electrode pairs were activated in temporally nonoverlapping manner. Two multichannel cochlear implant patients participated in the study. The method of magnitude estimation was used. Loudness growth for each electrode pair was first determined. The loudnesses of each electrode pair in a multielectrode pair stimulus were always set equally loud. The results showed that: (a) loudness increased with current level and the number of electrode pairs within a stimulus; (b) loudness summation for stimuli containing two electrode pairs was complete when the electrode pairs were approximately four electrodes apart (3.00 mm); and (c) loudness summation for stimuli containing three or four electrode pairs was incomplete in comparison to the results obtained for stimuli containing two electrode pairs. [Work supported by NIH Contract NOI-NS-9-2400 and NIH Grant NS21027.]
Speech feature encoding through an electrotactile speech processor Robert
Authors: Cowan S. C. , Blamey Peter J. , Alcantara Joseph I. , Whitford Lesley A. , Clark Graeme , Plant Geoff
Published: October 2005

Efficiency of speech feature encoding by the University of Melbourne multichannel electrotactile speech processor was assessed through performance of eight subjects on a closed-set tactual test battery. The battery consisted of 12 subtests, each assessing discrimination of a particular speech feature in an ABX paradigm. All subjects scored significantly above chance on suprasegmental features such as syllable number, stress, and vowel length. Discrimination of vowel formant contrasts was significantly above chance for seven subjects. Discrimination of consonant manner varied across specific subtest contrasts, with better encoding of the high-frequency fricatives and affricates. Discrimination of initial voicing contrasts suggested that tactual encoding of this feature could be improved. Comparison of these results with test battery scores from five different subjects with five commercially available tactile devices showed superior encoding of vowel formant and manner contrasts by the Tickle Talker. Subsequent consonant confusion studies with two hearing-impaired adults, one using tactual input in combination with lipreading and one in combination with aided residual hearing and lipreading, confirmed that added tactual information reduced the proportion of manner confusions and to a lesser extent voicing confusions.
Active control of panel-radiated noise using multiple piezoelectric actuators
Authors: Wang B. T. , Dimitriadis E. K. , Fuller C. R.
Published: October 2005

The potential for active control of structurally radiated nosie by two-dimensional piezoelectric patches bonded to the surface of thin elastic panels is analytically investigated. A previously presented approximate model for the loads induced by piezoelements bonded to the plate surface is employed for the calculation of the vibration and sound radiation from simply supported rectangular panels. The piezoelectric action modifies the vibration and hence effects the noise radiated by the panel when excited by constant distributed external forces. The complex amplitude of the voltage applied to the piezoelectric is estimated via an optimization scheme that minimizes the total radiated acoustic power into the farfield. Results have been obtained for a single as well as for multiple independently controlled actuators. It is seen that quite significant control is possible in some cases with a single appropriately taylored actuator. The effectiveness, however, deteriorates as control of higher vibration modes is attempted. Much better results are achieved with two or more independently controlled actuators bonded to the plate. It is clearly shown that multiple, appropriately positioned actuators drastically reduce undesired control spillover to the residual modes. [Work supported by ONR.]
Coupling effects between a lumped vibrational source of finite impedance and a plane radiator
Authors: Trentin Dominique , Berry A. , Laville Frederic
Published: October 2005

A typical situation in structural acoustics and vibrations is the case of a mechanical source of vibrations attached to a large, thin structure (radiator). In general, the force input into the structure, responsible for undesired vibrations of, and radiation from, the structure, is the resultant of both the output impedance of the source and the input impedance of the structure. A theoretical analysis of the problem is presented in the case of a lumped mechanical source composed of masses, springs, and dampers, with one single attachment point to a baffled, thin, rectangular, plane structure. The coupling assumes only pure transverse force transmission into the structure. A quadrupole approach for the source assembly and a variational approach for the motion of the structure allow, respectively, the source output impedance and the structure input impedance to be calculated in a variety of configurations. The force input into the structure, kinetic energy of the structure, and radiation of sound from the structure can then be derived. It is shown how the natural frequencies of the combined system can be found from the natural frequencies of the source and structure decoupled. Numerical results are presented for the particular application of optimal suspension design of mass-type source. [Dr. I. Michaluk is acknowledged for fruitful discussions.]
Active control of flexural power flow in beams using piezoceramic actuators
Authors: Gibbs Gary , Fuller Chris
Published: October 2005

Previous research has demonstrated that the flexural power flow in thin beams can be attenuated using active point force inputs [C. R. Fuller and L. O. Gonidou, “Active vibration control of flexural power flow in beams,” J. Acoust. Soc. Am. Suppl. 1 84, S47 (1988)]. In this paper, the results of experiments that demonstrate the feasibility of using surface-bonded piezoceramic actuators and sensors in controlling vibrational power flow in elastic structures are presented. The control system utilizes both a piezoceramic control actuator and sensor, and a time domain least-mean-squares adaptive algorithm to minimize transmitted power flow. Both semi-infinite and finite beams of various geometries are considered, and the results show significant reduction of vibrational power flow using only a single piezoceramic transducer as the control actuator. [Work supported by NASA Langley Research Center.]
Vibration and stability of an elastic beam subjected to a periodic axial load with time-dependent displacement excitation at both ends
Authors: Wu Xiao-Feng , Akay Adnan
Published: October 2005

This paper considers the vibration and stability of an elastic beam under the excitation of a combined periodic axial load and time-dependent displacement at its ends. Such problems are often encountered in the prediction of noise radiation from high-speed planar mechanisms with elastic couplers. The governing equation of motion for the vibrating beam derived by the Hamilton's principle is highly nonlinear. To obtain an approximate solution, the method of assumed modes is used. The equation of motion then reduces to a Hill type of equation in time. The parametric studies of the stability of the beam is carried out. The stable and unstable regions of the beam vibrations under the time-dependent displacement excitations are investigated. The independent restraint motions at the ends of the beam are described by the displacement influence functions. The total response is finally obtained by adding the relative motion of the beam under the given boundary conditions to the specified displacement at its ends.
Analysis of sound transmission through flexible panel/frame walls
Authors: Bliss Donald B.
Published: October 2005

Low-frequency sound transmission through flexible panel/frame walls is an important noise control problem, particularly for propeller aircraft interior noise. The coupled structural/acoustic problem for spatially periodic structures is solved using a multiple-scale perturbation expansion, based on the scale separation between panel size and acoustic wavelength, and an averaging procedure applied over the rapidly varying (panel) scale. A composite solution is formed from a smoothed global solution and a periodic local solution that accounts for the detailed panel motions. The panel subsystems appear in an averaged sense in the global solution through transfer functions, obtained from the local solution for distributed frame loadings and acoustic boundary conditions. Walls composed of identical panel subsystems, each containing several different panels, attached to a flexible frame, can be analyzed. This arrangement allows for noise reduction by alternate resonance tuning (ART), in which adjacent panels are tuned to resonate alternately above and below the frequency to be attenuated, with the resulting out-of-phase motion producing acoustic cancellation. Solutions are presented for a model problem involving sound transmission through a panel/frame wall and compared with the exact solution to assess the accuracy of the perturbation method. Noise reduction by ART is demonstrated by using two panels with different resonant frequencies in each subsystem. [Work supported by NASA Langley Research Center.]
Acoustic radiation of stiffened shells covered with a layer of slightly compressible material
Authors: Laulagnet B. , Guyader J. L.
Published: October 2005

This work deals with the calculation of sound radiation from a shell covered with a layer of slightly compressible material and immersed in water. In this case, the assumption of locally reacting material is unrealistic, and a more elaborate model must be used to describe the behavior of the coating layer. This has been achieved by solving the equations of elasticity in cylindrical coordinates, and by use of asymptotic expansions. The layer displacements and stresses are then coupled to the shell displacements and fluid loading on the boundary surfaces. The calculation of shell radiation is made using the normal modes of the in vacuo basic shell, and the asymptotic expansion truncated to the second order. Numerical results are presented showing the influence of layer thickness, damping, and Poisson ratio. [Work supported by D.R.E.T. and C.E.R.D.A.N., Ministère de la Défense.]
A new efficient Ritz vectors technique to solve elastoacoastic problems
Authors: Coyette J. P.
Published: October 2005

Solution of interior elastoacoustic problems in the frequency domain is addressed through an efficient nonmodal approach. The procedure relies on a symmetric two-field formulation (displacement variables are selected for the structure, while velocity potential is used for the acoustic medium). The related second-order system is transformed into a first-order one by doubling the size of the system. An updated Ritz vectors process allows the generation of two coupled bases, which enables the accurate description of both structural and acoustic responses. Details about the generation of these vectors are provided. The process requires only the solution of the static problems and the performance of basic orthogonalization and scaling operations. The resulting high-vectorization ability is stressed. Comparisons with conventional modal synthesis procedures are provided in order to show the efficiency of the proposed approach. It is shown that the selection of this technique leads to an optimal solution scheme. Various numerical results related to Guy's problem (cavity backed plate} are reported. Extensions to deal with structural and/or acoustic damped cases are also reported.
Effect of backlash and sleeve bearing clearance on the vibration spectrum of high-speed spur gear boxes
Authors: El-Saeidy Fawzi M. A. , Youshimura T.
Published: October 2005

An analytical model is presented to simulate the effects of tooth backlash and sleeve bearing clearance on the vibration spectra of high-speed spur gear boxes. Elasticity in bending and torsion of the shafts, time-varying mesh stiffness, tooth backlash, and Hertzian mesh damping, friction between engaged teeth, and interaction between gear box casing and internals are accounted for. During contact between journal and bearing, where time-varying contact stiffness with consideration of damping at contact point is accounted for, bearing clearance, system vibration, and bearing forces are calculated. The analysis is applied to a single stage gear box and equations of motion are numerically integrated to obtain system response in the time domain. The response is transformed into frequency domain using a fast Fourier transform (FFT) algorithm and samples of the results are shown for different values of backlash and bearing clearance.
On the vibration spectrum of high-speed spur gear boxes
Authors: El-Saeidy Fawzi M. A.
Published: October 2005

An analytical model is presented to simulate the effect of tooth backlash and ball-bearing radial clearance on the vibration spectrum of high-speed spur gear boxes. Included in this model are elasticity in bending and torsion of the shafts, friction between meshing teeth, interaction between gear box casing and internals, and time-varying tooth backlash, mesh stiffness (stiffness is calculated based on the strain energies of the tooth, which is treated as a cantilever beam of involute shape), and Hertzian mesh damping. The bearing loads are calculated with consideration of shaft oscillations and speed, bearing radial clearance, ball centrifugal force, and bearing outer ring oscillations. To demonstrate the model, a single stage gear box is analyzed, and equations of motion are numerically integrated to obtain system response in the time domain. This response is transformed into the frequency domain using a fast Fourier transform (FFT) algorithm and samples of the results are shown for different values of backlash and bearing clearance.
The acoustics of the external ear: Old problems and fresh perspectives
Authors: Shaw E. A. G.
Published: October 2005

A coherent picture of the external ear, operating both in the free field and as an enclosed receiver, came into focus more than a decade ago though several troublesome problems remained, particularly at frequencies greater than a few kHz. These included uncertainty about the geometry and acoustical characteristics of the ear canal, uncertainty about the dynamics of the eardrum and the reflection of sound from the eardrum, uncertainty about the role of the external ear in sound localization and, above all, uncertainty about the acoustical interactions between earphones and ears. Considerable progress has been made in most of these areas during the past few years but some problems remain intractable. In the meantime, the scientific and technological advances of the 1970s and early 1980s have provided us with a legacy of valuable instruments: eardrum simulators, artificial heads especially the Knowles Electronic Manikin (KEMAR), microphones for probing ear canal pressure, and improved insert earphones.
Optimization of hearing-aid gain and frequency response for cochlear hearing losses
Authors: Leijon Arne
Published: October 2005

A new theoretical procedure was developed for optimizing the acoustic characteristics of hearing aids. The algorithm increases predicted speech intelligibility while keeping the estimated loudness of amplified speech at a predetermined level. The intelligibility criterion was the mutual information between spoken phonetic messages and the corresponding streams of auditory patterns in a psychoacoustic model of the listener's auditory system. The speech signal was modeled as a sequence of allophone transitions. Each transition was represented by three auditory patterns, each containing ten cepstrum coefficients, one voice and one duration parameter. The shape of optimized hearing-aid frequency responses depended strongly on the desired loudness of amplified speech. When normal loudness was desired for speech at 65 dB SPL, and the optimization was initialized with the NAL prescription, hearing-aid gain was reduced, but predicted speech intelligibility was nearly unchanged. Predicted intelligibility of amplified speech in a noisy background was similar for several different frequency responses. The mutual information was highly correlated with a modified version of the articulation index.
Further studies of the underwater noise produced by rainfall
Authors: Elmore Paul A. , Pumphrey Hugh C. , Crum Lawrence A.
Published: October 2005

A study of the sound produced by water drops striking a water surface has confirmed some earlier results [Pumphrey et al., J. Acoust. Soc. Am. 85, 1518 (1989)]. In particular, for a certain well-defined range of drop sizes and impact velocities, drops will predictably and repeatedly entrain bubbles; this phenomenon has been named regular entrainment. In the present study, various fixed drop diameters have been used to investigate how bubble frequency, dipole strength, and time between drop impact and bubble formation vary with impact velocity. It is found that as impact velocity is increased through the point where entrainment begins, both frequency and dipole strength decrease to a minimum value and then rise again as the highest velocity at which entrainment occurs is approached. Both terms show increased variability near the critical upper and lower velocities. The frequency tends to increase monotonically as drop size is reduced; drops that entrain bubbles at their terminal velocities tend to produce frequencies near 14 kHz, which is also the peak frequency of the natural rainfall spectrum. Finally, the time between drop impact and bubble formation was found to increase monotonically as drop size or impact velocity increases. [Work supported by Office of Naval Research.]
Underwater sound generated by impacts and bubbles from raindrops at oblique incidence
Authors: Kurgan Armagan , Medwin Herman , Nystuen Jeffrey A.
Published: October 2005

The sound generated by rainfall at sea is caused by raindrops of a wide size range that fall at their terminal velocities and generally strike the ocean surface at local, oblique incidence. Laboratory experiments have been conducted to evaluate the energy spectrum of sounds caused by both the impact and the bubble formed by single raindrops. The results, using terminal velocities and oblique trajectories, are very different from the published normal incidence, nonterminal-velocity characterizations. For example, bubble frequencies other than the well-known 14-kHz peak are found. Also, the energy of the impact sound increases significantly for larger drops and for large deviations from normal trajectories. These observations provide specific reasons for the known broadening of the 14-kHz spectral peak of rain noise in the presence of winds at sea. [Work supported by ONR.]
Acoustical measurements of spectral rates of bubble production under spilling breakers
Authors: Daniel Albert C. , Medwin Herman
Published: October 2005

It has been shown that spilling breakers in the laboratory produce a variety of bubbles whose total incoherent intensity is the Knudsen sea noise spectrum from 1 to 20 kHz [H. Medwin and M. M. Beaky, J. Acoust. Soc. Am. 86, 1124–1130 (1989)]. By using a hydrophone to simultaneously trigger both a “computerscope” and a spectrum analyzer, it is now possible to positively identify near-surface bubbles and to count their rate of production per unit area of the breaking wave. This passive acoustical determination spans a much greater range of bubble radii, with a radius resolution that is an order of magnitude finer than optical measurements [e.g., Y. Toba, Mem. Coll. Sci., Univ. Kyoto, Ser. A, XXIX(3) (1961)]. [Work supported by ONR.]
Effect of internal solitons on shallow-water sound propagation
Authors: Zhou Jixun , Zhang Xue-zhen , Rogers Peter
Published: October 2005

There have been many reports on observations of naturally occurring internal solitary wavetrains (solitons) in the coast zone, especially in the summer. The mechanism for the generation of these nonlinear internal waves has been investigated in the geophysics and fluid mechanics community. Little attention, however, has been focused on their effect on sound propagation with the exception of the work of Baxter and Orr, which was based on ray theory [L. Baxter and M. H. Orr, J. Acoust. Soc. Am. 71, 61–66 (1982)]. In this paper, the parabolic equation (PE) model (IFD or PAREQ code) is used to numerically simulate the effect of internal solitons on low-frequency sound propagation in the coast zone. The results show that sound transmission loss is sensitive to soliton parameters (such as wavelength, amplitude, etc.) and wave packet parameters (position, number, and propagation direction). The results can be used to explain, at least partly, an interesting experiment phenomena: The frequency response of shallow-water sound propagation under the condition of a thermocline during the summer is often a strong function of space and time, and sound propagation over certain frequency ranges has an abnormal attenuation that cannot be explained by using conventional models of sound propagation. [Work supported by ONR.]
Simultaneous screech tone modes of an axially symmetric jet
Authors: Umeda Y. , Ishii R. , Powell Alan
Published: October 2005

The screech frequency of axially symmetric choked jets falls steadily with decreasing pressure ratio, with several frequency jumps, some up, some down [A. Powell, Proc. Phys. Soc. London Ser. B 66, 1039-1056 (1953)]. Davies and Oldfield's Lissajous figures [Acustica 12, 267–277 (1962)] showed that the corresponding jet oscillation modes are of various types. Schlieren photography and digitally processed acoustic pressure signals are now used. Unambiguously, the first two modes, a1 and a2, are axially symmetric (varicose, like ring vortices); the next, b, is asymmetric in an arbitrary plane (sinuous); c is helical, rotating in either sense, stable once started, while d is sinuous again, connected to c by hysterectic jumps. However, tone d is weakly but smoothly connected to b, so d appears to be an extension of b. Moreover, the dominant c tone extends weakly to overlap where b and d dominate, and a suspected weak a2(?) overlaps where b, c, and d dominate. Further, both a1 and b exist weakly where a2 dominates. Evidently jumps occur not necessarily at changes in the mode as previously thought, but when there is a change in which one dominates.
Recent experiments on impinging choked jet tones
Authors: Powell Alan , Henderson Brenda
Published: October 2005

Two modes of oscillation, L and S, associated with large and small plates were described, with frequency analysis by counter [A. Powell, J. Acoust. Soc. Am. 83, 515–533 (1986)]. With different slopes on log-log plots of wavelength versus nozzle-to-plate spacing h, feedback to nozzle and to stand-off shockwave, respectively, was hypothesized. Digital signal processing is more revealing! The same dominant and S tone are found, exactly. It now appears these L and S are the dominant members of classes of tones. At small h, for large plates (all pressures) and small plates (low pressures), L tones are observed in multiple modes, usually simultaneously. For intermediate h, frequency jumps occur; schlieren photography reveals symmetric and asymmetric jet flow oscillations. Nozzle reflector influence supports the feedback to the nozzle hypothesis for L. For large h at low pressures, three strong constant tones exist—screech a1 and a2—and one other(?). At higher pressures (small plates), S tones appear, influenced by a nozzle reflector (!); schlieren photographs exhibit symmetrical oscillations of jet and stand-off shockwave. For intermediate plates, both L and S classes occur.
On the feasibility of the evaluation of the performance of a pinger transducer in an open tank using a pressurized vessel
Authors: Bindal V. N. , Saksena T. K. , Gupta S. C. , Chaubey D. R.
Published: October 2005

Investigation on the calibration of pinger transducers to a hydrostatic pressure of 200 psi is described. The transducer is housed in a specially constructed vessel fabricated from fiberglass in polyester and epoxy matrix of 10-mm wall thickness. The insertion loss of the walls of the vessels has been estimated in the frequency range 10–20 kHz and is observed to be small. Source level measurements have been made by putting the pressurized vessel in a tank of dimension 6.35 m × 5.85 m ×2.2 m3. The merits and demerits of the vessels using an epoxy and polyester base have been discussed. Measurements show that there is no significant variation in acoustic output of the pinger transducer up to 200 psi, although a variation is observed in the frequency response characteristic. The method is suitable for characterization of a transducer at high pressures that cannot be characterized by using conventional techniques.
The physics model of thyristor interference in radios and other communication equipment
Authors: Yang Ming-Fu , Xue Fei , Lu Yi-Pei
Published: October 2005

With the increasing use of thyristors in electric installations such as lamp controllers, electric fan controllers, and electric heat controllers, thyristor interference in the middle frequency (f < 20 MHz) range is repugnant and seriously hampers the use of thyristors. A physical model of thyristors indicates that interference results from the instantaneous pulse that is produced when the thyristor is turned on. Such interference will produce an interference pulse on a nearby antenna that is received and amplified to become annoying noise. This conclusion is useful in the design of electric installations using thyristors so that such installations have greater reliability and better interference prevention.
Elastic constant reconstruction using resonances of coupled modes in thin anisotropic plates
Authors: Rokhlin S. I. , Wu C. Y. , Wang L.
Published: October 2005

At oblique incidence of ultrasonic waves on a thin anisotropic composite plate immersed in fluid, the quasilongitudinal, flexural, and quasi-SH vibrations are excited. At some angles of incidence, coherent interactions of these waves lead to minima of the normal displacement on the back surface of the plate and therefore to minima of the transmission coefficient. At off-axis orientations of the thin composite plate, two such minima may be observed. Their positions are only slightly dependent on frequency and are determined by plate properties and orientation. This effect was studied both theoretically and experimentally. The elastic constants have been reconstructed for a unidirectional graphite-epoxy composite plate from experimental data that have been taken at different plate orientations and frequencies.
Guided wave generation by direct excitation
Authors: Nagy Peter B. , Adler Laszlo
Published: October 2005

Guided acoustic waves along interfaces and more complex layered structures are often used in ultrasonic NDE. Their outstanding sensitivity to specific properties associated with interface conditions and bond quality is due to the fact that their energy is effectively confined to the region of interest. On the other hand, this advantage turns out to be a great drawback for generation and detection of such guided waves. Certain modes with higher phase velocity than at least one of the bulk velocities of the surrounding media are called leaky modes that can be coupled to via phase matching bulk waves. True guided modes of lower phase velocity than any of the bulk velocities of the surrounding media are much more difficult to generate and detect. A simple experimental technique based on longitudinal or shear wave excitation along the interface is shown to be very effective in generating both symmetric and antisymmetric guided modes of Rayleigh (SV) or Love (SH) type of polarization. Experimental results from different plates and adhesive and solid-state interfaces are shown to be in good quantitative agreement with theoretical calculations. This technique might find numerous applications in basic acoustic studies as well as ultrasonic nondestructive evaluation. [This work was supported by the Office of Naval Research under Contract N0014-C-2129.]
Consonant testing of a tactile hearing aid based on amplitude- and time-quantized speech
Authors: O'Brien Edward M.
Published: October 2005

Speech was first prefiltered with a second-order bandpass filter centered at 1.5 kHz. Speech was then amplitude quantized to two levels based on the zero crossings of the waveform. This signal was then time quantized such that it could only change states in association with a clock signal. The intelligibility of the processed speech remains high for clock frequencies above 10 kHz (which was the quantizing rate used for this study). The discrete digital frequencies in the resulting waveform were easily detected with a digital logic circuit. These were then displayed onto the skin of the abdomen with a linear array of concentric ring electrodes. Thirty-one electrodes (representing frequencies between 151 and 2500 Hz) were used for the array. Biphasic constant current pulses were used as the stimuli. Five normal hearing college age students served as the subjects. Discrimination of consonant pairs was used to test the ability of the tactile aid to transmit speech information to the subjects. The following ranges of accuracy (corrected for guessing) were observed: stops and constituents, 18% to 87%; voiced and unvoiced consonants, 3% to 27%; consonants with different places of articulation, 27% to 90%; nasal, glides, and semivowels, 17% to 49%.
Regression effects in magnitude judgments of line length, and vibrotactile sine and pulse loudness
Authors: Collins Amy A. , Cholewiak Roger W.
Published: October 2005

Five observers performed absolute magnitude estimation (AME) and absolute magnitude production (AMP) of line lengths and vibrotactile pulse and sine loudnesses as well as matching of each possible pair. Line lengths, presented visually, could extend over a 7- to 950-mm range. Vibrotactile stimuli were 32-pps haversine pulses and 250-Hz sinusoids presented to the palm with 7-mm diameter contactors and static surrounds. When the AME and AMP data were plotted together, perfect correlation was not seen indicating the influence of regression effects on the data. Regression effects occur when observers making judgments on two perceptual continua (i.e., line magnitude and number magnitude) restrict the range of their responses gravitating toward the mean response. Magnitude balance functions (MB) were calculated from AME and AMP data for the line, sine, and pulse. The cross-modality matches, made with each stimulus type serving as the standard, showed similar regression effects. These data are discussed with reference to transitivity and the relationships among the data set predicted from the absolute scaling hypothesis. [Work supported by NIH.]
Evidence for a tight blood-labyrinth barrier
Authors: Inamura Naoki , Salt Alec N. , Thalmann Ruediger
Published: October 2005

The entry of a small tracer ion (FW 135.6) from blood into perilymph and cerebrospinal fluid (CSF) has been monitored using ion-selective electrodes. The tracer, trimethylphenylammonium (TMPA) can be detected in extremely low concentrations (< 1 μm) by electrodes, allowing entry to be accurately quantified. Electrodes were sealed into the cochlea to ensure that artifactual fluid leakages did not distort the results. A constant level of TMPA in plasma (approximately 0.5 mM) was maintained by continuous venous infusion of tracer. TMPA entry into CSF was extremely slow, reaching only 13% of the plasma level within 90 min (n = 3). Tracer entered perilymph even more slowly, reaching 6.5% (n = 5) and 3.7% (n = 5) of the plasma level in 90 min for ST and SV, respectively. The slow entry of such a small ion into perilymph demonstrates the existence of a tight barrier between blood and perilymph, and eliminates the possibility that perilymph is generated by mechanisms such as ultrafiltration. In two animals where bleeding was noted at the electrode insertion site, a much more rapid rate of tracer entry was recorded, probably as a result of plasma leakage into perilymph. Treatment with epinephrine (giving a brief blood pressure increase) also opens the barrier, allowing rapid tracer entry.
Action potential tuning curves recorded with a derived response technique
Authors: Garcia Philip , Salt Alec N.
Published: October 2005

A number of laboratories use tonal masking methods in conjunction with the cochlear action potential (AP) to generate AP tuning curves. In these studies, the amplitude of AP elicited by a probe stimulus is monitored as the level of masker is varied. An amplitude reduction (AR) by a specified amount (25%–100%) is used to indicate masking of the response. An alternative method was investigated in which interaction of the probe and masker is monitored by digital subtraction of the unmasked and masked responses, generating a tone-derived (TD) response. An amplitude criterion of 10-μV TD response is used to indicate masker/probe interaction. Tuning curves were recorded from the round window of anesthetized guinea pigs using AR and TD methods. With near threshold probe stimuli, similar tuning curves were obtained. With higher levels however, markedly different results were observed. AR tuning curves became elevated and sharper while TD curves became lower and broader. The TD method appears to better represent the frequency spread of responses with increasing stimulus level as demonstrated at the single unit level. In addition, TD tuning curves were able to detect second harmonic distortions of the probe stimulus, while AR tuning curves did not. [Work supported by Program project grant P01 NS24372 and Training Grant NS 07278.]
Post-discharge recovery effects in gerbil auditory-nerve period and PST histograms
Authors: Bosch Walter R.
Published: October 2005

Excitation-function (EF) and recovery-function (RF) parameters of a self-exciting point process (SEPP) model for auditory nerve discharges were estimated [M. I. Miller, J. Acoust. Soc. Am. 77, 1452–1464 (1985)] for neural discharges recorded in gerbil in response to continuous-tone and tone-burst stimuli. The mean discharge intensity (MDI) of the SEPP model (expected value of the PST or period histogram) was computed from the EF and RF estimates by solving an integral equation [K. Jones et al., J. Acoust. Soc. Am. 78, 90–94 (1985)]. Period histograms computed from neural discharges in response to continuous-tone stimuli were found to agree almost exactly with the corresponding MDI over a range of stimulus sound-presSUre levels from 0 to 50 dB above threshold, indicating that the SEPP model accounts well for post-discharge recovery effects in period histograms under these stimulus conditions. PST histograms computed from the neural response to tone-burst stimulation also agreed quite well with the computed MDI for the conditions tested. [Work supported by NIH grants NS21592 and RR01379.]
Perceptual fusion of tonal and noisy sounds
Authors: Hermes Dik J.
Published: October 2005

If stationary noise is added to a tonal, periodic sound, the noise is, to a large extent, perceived as a separate sound coming from a source other than the periodic sound. Perceptual fusion of noise with a periodic sound requires specific conditions. Results will be presented that indicate that the temporal envelope of the noise plays an important role in this matter. In experiments in which this envelope had the same peridocity as the tonal stimulus, perceptual fusion did occur. Furthermore, the energy content of the noise within successive periods of the envelope was made more or less constant. These results were obtained in an experimental setup in which a quantitative measure was obtained for the extent to which the noise integrated with the periodic sound. It will be argued that perceptual fusion as reported here cannot be explained by a peripheral mechanism such as adaptation, but must be the result of a central process which groups components from a wide range of frequency bands into one or more sound images.
Vowel formant frequencies produced with and without auditory feedback
Authors: Tobey Emily A. , Murchison Christy
Published: October 2005

Several authors have hypothesized that auditory feedback is used to refine articulatory gestures in children developing speech. In order to examine the role of auditory feedback in children, vowel production was examined in 12 children ranging in age from 3–13 years who received a multichannel cochlear implant. Data were collected 1 year after using the implant. Speech samples consisted of ten repetitions of the word, “head,” spoken under four conditions: implant on, immediately after the implant was turned off, 20 min after nonuse, and immediately after the implant was turned on. Formant frequencies, fundamental frequencies, and duration were measured. Significant shifts in vowel formant frequencies were found when the implant was turned off (p < 0.0001) and returned to more nearly normal values when the implant was turned on. Two of the youngest subjects were unable to produce stimuli after 20 min of nonuse with the implant. Data support the hypothesis that auditory feedback may assist in refining the articulatory gestures of some speech sounds.