bluuebunny/crossref_metadata_2025 huggingface dataset:
Amplitude-modulation depth discrimination of a sinusoidal carrier.
Authors: Lee Jungmee , Bacon Sid P.
Published: October 2005

Discrimination of the change in depth of sinusoidal amplitude modulation was investigated for a 4000-Hz carrier. The just noticeable change in the modulation depth (Δm) was measured as a function of (1) standard modulation depth (m = 0.1, 0.18, or 0.3), (2) modulation rate (fm=10, 20, 40, or 80 Hz), and (3) stimulus duration (T=25, 50, 100, 200, 400, or 800 ms). For modulation rates less than 80 Hz, threshold (Δm) was higher at a standard depth of 0.3 than at the other standard depths. When fm=80 Hz, the threshold was almost the same across different standard modulation depths. For all standard depths and modulation rates, the threshold decreased by more than a factor of 2 as stimulus duration increased to a certain T (critical duration). For durations longer than the critical duration, the threshold decreased only slightly or remained constant. The critical duration corresponded to about four cycles of modulation. Psychometric functions were measured for different stimulus durations. The data were evaluated in terms of a multiple-looks model. [Work supported by NIDCD.]
Effects of noise on the hearing system.
Authors: Chung King
Published: October 2005

This paper provides an overview of effects of noise on the hearing system. Animal research has shown that excessive noise exposure results in decrease of blood flow in stria vascularis, alteration in permeability of ions in reticular lamina, swelling/rupture of hair cells, disarrangement or loss of stereocilia, broken tip links and side links between the stereocilia, swelling of afferent dentrides, rupture of the organ of Corti, decrease in tectorial membrane thickness, and increase in its compliance, etc. After the exposure, the stereocilia may become a fanlike structure or fuse together to form a giant stereocilia. In a severely damaged cochlea, the hair cells may be replaced by some undifferentiable scar tissue. The pharyngeal processes of the Deiter’s cells and other supporting cells enlarge to seal off the endolymph and perilymph ion boundaries. The neural fibers and ganglion cells may gradually degenerate and tonotopic reorganization in dorsal cochlear nucleus follows. Along with these anatomical damages, physiological changes include disruption of the cochlear active process, changes in cochlear potentials, broadening of the turning curve of basilar membrane and spiral ganglion neurons, and hearing loss are also observed. Remedial procedures, e.g., regeneration of hair cells and ‘‘preexposure conditioning‘‘ are also discussed.
The foundation of the Institute of Sound and Vibration Research.
Authors: Davies Peter O. A. L.
Published: October 2005

There are few people for whom a flourishing research institution provides a living memorial. That the ISVR was born at all was due to the characteristic and legendary ‘‘ten-year vision‘‘ of its founder, Professor Elfyn Richards. In the 1950’s, as Professor of Aeronautics at Southampton, he perceived that noise and vibration were to become a ‘‘disease’’ of new technology, for which traditional approaches would be no cure. Thus he founded a new applied science, now known as engineering acoustics and vibration. This memorial paper describes the first two decades of both the foundation and early development of the ISVR. It concludes with a brief appraisal of its current activities.
Jet noise: The early history.
Authors: Lilley Geoffrey M.
Published: October 2005

The invention of the jet engine and its development during World War II as the propulsive system for fighter aircraft led aircraft designers in the late 1940s to investigate its use as the power plant for civil air transports. The aim was improved speed, economics, and efficiency over that of slower propellor-driven aircraft. However two major problems existed, (a) its high fuel consumption, and (b) its noise at full take-off power. Innovative University jet noise research in the UK in the late 1940s and early 1950s quickly led to strong industry–university collaboration. This resulted in the development of the corrugated or lobed nozzle for jet noise reduction and later to the introduction of the bypass engine achieving significant reductions in both specific fuel consumption and jet noise reduction. The experiments by R. Westley and G. M. Lilley at Cranfield and by Professor E.J. Richards and A. Powell at Southampton University, Professor Sir James Lighthill’s theoretical studies at Manchester University, and the skill of F.B. Greatrex and his team at Rolls-Royce all contributed to this successful revolution in civil aircraft design. The paper discusses the rapid development of this early jet noise research and the corresponding complementary work in the USA.
Encounters I had with Professor Richards.
Authors: Maidanik G.
Published: October 2005

I met Professor Richards for the first time in 1951, when I was considering Southampton University for undergraduate studies. He never remembered it, I have. The second time I met Professor Richards was in 1962 in Boston, and then again and again over the subsequent years. I was always impressed by his keen scientific sense and his friendliness, the mark of a great educator, which he certainly was.
Open set speech recognition in congenitally deaf children using a multichannel cochlear prosthesis.
Authors: Waltzman Susan
Published: October 2005

Thirty-eight congenitally deaf children received the Nucleus multichannel cochlear prosthesis at NYU Medical Center prior to age five. Preoperative and postoperative evaluations included pure tone audiometry under earphones, warble tone audiometry in the sound field (amplification system preoperatively and implant postoperatively), and open set measures of word/sentence recognition. Tests administered included, but were not limited to, GASP words and sentences, PBK words (scored as words and phonemes) and Indiana phrases and were administered preoperatively and 6, 12, 18, 24, 36, 48, and 60 months postoperatively. Results indicated a significant improvement over time in the ability of the children to perceive words and sentences in the implant only condition. Percent correct scores improved with length of usage and increasing age, reflecting increased ability of the young children to perform the necessary tasks, in addition to developing speech recognition abilities. After using the device for two or more years the children had varying degrees of open set speech perception. These results demonstrate significant improvement in open set speech perception in congenitally deaf children implanted below the age of five.
Lexical discrimination and age at implantation.
Authors: Kirk Karen Iler
Published: October 2005

Recent research suggests that prelingually deafened children implanted at an early age may obtain greater speech perception and language benefits than those children implanted at a later age. This investigation examined word recognition and lexical discrimination in pediatric cochlear implant users as a function of age at implantation. Two groups of prelingually deafened children who used the Nucleus multichannel cochlear implant participated in this study. The first group contained children who received their device between the ages of 2–5 years, and the second contained children who were implanted between the ages of 6–9 years. Speech perception performance was evaluated using a new measure, the Lexical Neighborhood Test, a traditional measure of word recognition, the PBK, and a measure of receptive language abilities (the PPVT or the Reynell Developmental Language Scales). Children implanted at a younger age had better word recognition performance and were better able to identify lexically difficult words (i.e., those that occur infrequently and have many other phonemically similar words with which they can be confused). Correlations with vocabulary and language performance will also be reported. [Work supported by NIDCD DC00064.]
Conjugate mirror array performance in the presence of surface and bottom roughness.
Authors: Ewart Terry E. , Rouseff Daniel , Jackson Darrell
Published: October 2005

Dowling and Jackson [J. Acoust. Soc. Am. 91, 3257–3277 (1992)] provided a study of the temporal/spatial effects of an internal wave field on phase conjugate arrays. In the present work the effects of interface roughness on phase conjugate arrays are simulated. The stochastic surface wave field is generated to include realizations of the sea surface height that evolve in time. The time variability of the surface also includes the effects of the acoustic travel time, so that each realization is ‘‘as viewed’’ in the frame of the acoustic wave from source-array-to-receiving-array and the return after phase conjugation., The acoustic wave propagation is accomplished using a parabolic equation marching algorithm that includes this random rough surface. Bottom penetration and absorption are included. Coupling of the surface wave field with the bottom/sub-bottom randomness can produce an increased degradation of the return field. Thus even if the processing time to produce the conjugate field approached zero, degradation of the conjugate array focus will occur. A discussion of the relevance of this work to conjugate array applications will be presented. [Work supported by ONR.]
Travel time variability and localization accuracy for global scale monitoring of underwater acoustic events.
Authors: Farrell Ted , LePage Kevin D.
Published: October 2005

Large amplitude underwater acoustic signals, such as those produced by earthquakes and nuclear tests, can be monitored on a global scale using a limited network of underwater acoustic sensors. The design and operation of such a network requires an understanding of the limits on localization accuracy due to sound speed fluctuations in the ocean. For localization based on time of flight, the variance of the arrival time of the individual modes may be estimated by a range and depth integral over the sound-speed fluctuation statistics of the water column. Results obtained for travel time variance using this approach are compared to simpler measures such as the variance of the sound axis slowness integrated over a geodesic path. These results are in turn utilized to estimate the localization areas of uncertainty for a variety of source and receiver scenarios. All results are based on measured sound-speed statistics obtained from various ocean databases. [Work supported by DOE and Air Force Phillips Laboratory.]
Performance of desert kit foxes, Vulpes macrotis arsipus, on acoustic detection trials during simulated jet aircraft overflights.
Authors: Bowles Ann E. , Yaeger Scott , Kugler B. Andrew , Golightly Richard
Published: October 2005

Two male and female desert kit foxes were exposed to simulated prey and predator sounds in the presence of aircraft noise to determine detection rates. They were tested in a 9.75×9.15-m outdoor pen in the dark. Five feeding stations were equipped with speakers to play scratching sounds (prey noise) and a single speaker outside the pen projected stealthy footsteps (predator noise). Foxes approached feeding stations projecting prey noise to receive a reward; they spontaneously avoided predator noise. Foxes were exposedto 980 simulated low-altitude jet overflights in the range from 65 to 95 dB ASEL. Stimulus sounds were played for 1 min at the limit of detection; the longest simulated overflight was 45 s. Fox performance was compared with and without simulated aircraft noise (309 and 110 trials, respectively). Foxes exhibited flight reactions or dropped flat during initial exposures. Within 1–2 series of exposures, these responses habituated, although milder reactions persisted. Foxes identified the correct feeding station 63%–71% of the time (chance rate=20%) in silence versus 24%–30% in noise. They detected predator sounds on 81%–83% of trials, regardless of noise. The results suggest that foxes listened for potential predators preferentially in the presence of aircraft noise. [Work supported by USAF NSBIT Program, Contract F33615-90-D-0653.]
Effects of underwater sound on hair cells of the inner ear and lateral line of the oscar (Astronotus ocellatus).
Authors: Hastings Mardi C. , Popper Arthur N. , Finneran James J. , Lanford Pamela J.
Published: October 2005

Fifty-nine oscars (Astronotus ocellatus) were subjected to pure tones at 60 or 300 Hz in order to determine the effects of sound at levels typical of man-made sources on the sensory epithelia of the ear and the lateral line. Sounds varied in duty cycle (20% or continuous) and sound-pressure level (100, 140, or 180 dB re: 1 μPa). Fish were allowed to survive for one or four days post-treatment. The study also included five control animals that were handled in the same way as the test animals, but were not exposed to any sound. Tissue was then evaluated using scanning electron microscopy to assess the presence or absence of ciliary bundles on the sensory hair cells in each of the otic endorgans and the lateral line. Damage was found in four of five fish stimulated with 300-Hz continuous tones at 180 dB and allowed to survive for four days. It was limited to small regions of the striola of the utricle and lagena. No damage was observed in fish that had been allowed to survive for one day post-stimulation, suggesting that physical signs of damage may develop slowly after exposure. [Work supported by ONR.]
Discussion and demonstration of PC CITASAN.
Authors: Sharp Paul A.
Published: October 2005

PC CITASAN is a software program that contains a database of over 4500 references to scientific literature on the impact of aircraft noise and sonic booms on humans, animals, structures, and noise modeling. It contains bibliographic data and a suitability rating and a controversiality rating for each article. Some articles also have an abstract and an independent review. The data were updated as of Nov 1994. The PC CITASAN database can be searched using four different pre-defined screens, one for each impact category. The search can be global, by author, by key words in the title, or by year of publication. The program was developed for use by USAF personnel preparing environmental assessment documents. However, it has broad application to other government, civilian, academic, and commercial organizations. The program was originally written to operate under the UNIX operating system using ORACLE as the database. It has been completely re-written to run under the Windows environment on a PC as a stand alone system and does not require a dedicated database. It will be distributed on a CD-ROM with a hardcopy user’s manual.
Field methods for measuring auditory function in wild animals.
Authors: Bowles Ann E.
Published: October 2005

Laboratory characterization of auditory sensitivity in wild vertebrates is typically based on measurements from a small number of relatively healthy and young individuals. The auditory sensitivities of animals in populations are likely to vary greatly; individuals will vary in sensitivity at birth, and will experience diminished capacity due to injuries, noise exposure, age, starvation, reproductive stresses, parasites, etc. Although disabilities might be fatal for hearing-dependent species, such as nocturnal animals, healthy individuals with profound loss are sometimes found. Hypotheses about the adaptive value of hearing cannot be addressed without techniques to measure animal hearing quickly and accurately in field situations. While conditioning (‘‘behavioral’’) studies are the ‘‘gold standard’’ against which other techniques are evaluated, they cannot be used easily in the field. Examples of other techniques will be given and compared with behavioral measures for the same or similar species. These are (1) reflex modification (startle inhibition) used on 4 kit foxes (Vulpes macrotis) and 4 Merriam’s kangaroo rats (Dipodomys merriami), (2) auditory brain-stem responses used on 16 kangaroo rats and 12 desert tortoises (Gopherus agassizii), and (3) envelope-following responses used on a desert tortoise and a harbor seal (Phoca vitulina).
Sensitization and habituation to underwater sound by captive pinnipeds.
Authors: Kastak David , Schusterman Ronald J.
Published: October 2005

Responsiveness of three species of pinniped to two types of brief (5-s duration) underwater sound was investigated. The experimental stimulus was a broadband pulsed sound (peak levels of 110–135 dB re: 1 μPa). The control stimulus was a frequency sweep (rms level of 125–130 dB re: 1 μPa). Reactions were classified as avoidance or approach. Two California sea lions and a harbor seal showed no avoidance reaction to either stimulus. A northern elephant seal showed a powerful avoidance response to the pulsed sound and showed little reaction to the frequency sweep. The sea lions and harbor seal clearly showed habituation to both sounds. However, rather than showing habituation, the elephant seal showed sensitization to the experimental stimulus, as well as to the entire experimental setup. That is, as the experiment progressed, avoidance response to the signal was faster and duration of post-stimulus haulout behavior increased. In fact, following successive presentations of the pulsed sound, it was often not possible to coax the elephant seal back into the water. The results suggest that there are species-specific constraints on habituation to certain types of environmental stimuli.
Problem areas in predicting community noise that affect accuracy.
Authors: Brittain Frank H.
Published: October 2005

In theory, predicting community noise levels is relatively easy — once the needed information can be found. While the equations needed to formulate a noise prediction model are in the literature, unfortunately, they are spread between many references. Adequate information on noise levels of sources — either as sound-pressure or power levels — is often not available in the literature. Further, transmission loss data at low frequencies are not usually available. When one gets around these problems, another set of problems arises that is related to the accuracy of the models developed. These problems include source size and directivity, barrier and screening effects of equipment, reflections by equipment and buildings, piping and minor equipment, atmospheric and ground effects, and effectiveness of noise control barriers. Typical prediction technology is summarized. Problem areas that affect accuracy of noise predictions are identified and discussed.
New pressure measurements of elasticity using the rectangular parallelepiped resonance method.
Authors: Isaak Donald G. , Anderson O. L. , Carnes J. D. , Cynn H.
Published: October 2005

The rectangular parallelepiped resonance (RPR) method has proven to be an effective means to measure the adiabatic elastic moduli, Cij, at very high temperatures. The extension of the RPR technique to elevated pressure is an attractive proposition because bonding problems associated with coupling between transducers and specimens are essentially eliminated. However, RPR data have not yet been reported at elevated pressure because of (1) the small frequency shifts observed over the accessible pressure range, and (2) complications in the data reduction scheme by which primary measurements of a resonance spectrum are interpreted in terms of the specimen Cij’s. The experimental and analysis problems encountered when pressure dependences of modal frequencies are measured will be discussed, and ways in which these problems can be overcome will be presented. A new apparatus in which RPR measurements at elevated pressure have been made will be described. Initial RPR pressure data on several materials will be presented and compared to results obtained when using thermodynamic considerations that relate the temperature dependences of the resonant frequencies to their pressure dependences.
Resonant ultrasound spectroscopy investigation of a first-order
structural phase transition in LiKSO4.
Authors: Willis F. A. , Leisure R. G.
Published: October 2005

Lithium potassium sulphate (LiKSO4) exhibits a rich variety of structural phase transitions. Ten different phases have been reported over the temperature range from approximately 4 to 1000 K. The room temperature phase is hexagonal P63. On cooling, the room temperature phase transforms at approximately 205 K to another phase which is now believed to be trigonal P31c, although the symmetry of this phase has been controversial. Resonant ultrasound spectroscopy has been used to measure the complete set of elastic constants of LiKSO4 over the temperature range of 200 to 300 K. The room temperature elastic constants are accurately described by hexagonal symmetry. At approximately 213 K on cooling there are large abrupt changes of as much as 80% in many elastic constants. The elasticity of this phase cannot be described by hexagonal symmetry, but trigonal symmetry fits the data well. The elastic constants return to the hexagonal values at approximately 243 K on warming. The results will be discussed in terms of Landau theory. [Research supported by NSF under Grant No. DMR-9501550.]
Ultrasonic spectroscopy techniques used by dolphins to characterize resonating submerged elastic shells.
Authors: Gaunaurd G. C. , Brill D. , Huang H. , Moore P. W. B. , Strifors H. C.
Published: October 2005

The pulsed echoes returned by several submerged cylindrical shells insonified by the peculiar sound pulses (‘‘clicks‘‘) emitted by dolphins have been examined. These clicks and echoes were collected in a large database as is done in standard dolphin experiments [Animal Sonar: Processes and Performance, edited by P. Nachtigall and P. W. B. Moore (Plenum, New York, 1988)]. The emphasis here is on the processing and physical interpretation of the ultrasonic spectroscopic features in these dolphin-generated echoes. These resonance features actually permit the total characterization of the shells. The spectroscopic ‘‘lines’’ (i.e., resonances with widths) in the frequency signatures, as well as other features in the associated time-domain signatures, provide all the ingredients required to determine the size, shape, thickness, shell elastic material, and internal filler material, in all cases. The time and frequency processing of the echoes is explained in detail; it follows the pattern briefly outlined elsewhere [G. C. Gaunaurd, J. Opt. Eng. 31, 2253–2261 (1992); G. C. Gaunaurd and H. Huang, J. Inverse Problems Eng. (in press, 1996)], and it will be illustrated with many measured and computationally predicted graphs. These techniques may provide the basic physical explanation of the dolphin’s amazing target-ID feats.
Characterization of inertial confinement fusion targets.
Authors: Asaki Thomas J. , Hoffer James K. , Sheliak John D.
Published: October 2005

Prototype inertial confinement fusion targets for the proposed National Ignition Facility are metallic or plastic spherical shells (2 mm o.d., ≊150-mm thickness) with an ≊80-mm-thick layer of solid deuterium–tritium (50/50 mixture) deposited on the inner surface. Ignition will occur only if the D–T fuel layer meets strict sphericity and surface roughness criteria (typically ≊1 mm). Symmetric layering of solid D–T occurs due to the phenomenon of ‘‘beta layering’’ in which tritium-induced self-heating drives the redistribution of material. In contrast to the optical techniques usually employed, this work discusses methods in which resonant ultrasound spectroscopy (RUS) and related techniques can be used to help determine the uniformity of the fuel layer inside opaque targets. A tetrahedral array of pinducers in a cryogenic apparatus is used to both mount and probe the sample. Preliminary efforts have focused on the characterization of solid spheres and both aluminum and beryllium shells. Sufficiently high Q’s (103−105) necessary for detailed work are readily obtained. Studies involving deuterium-filled shells include the observation of liquid condensation, triple point measurement, and the effects of thermally induced redistribution.
Mechanical responses of the basilar membrane.
Authors: Nuttall Alfred L.
Published: October 2005

The traveling-wave activity that Georg von Békésy studied in the cochlea early in this century has been of intense interest to physiologists and mathematical modelers over the last 30 years. This interest was nurtured by the discovery that the mechanical responses of the basilar membrane are nonlinear at relatively low sound levels and that the nonlinearity is dependent on biological processes [W. S. Rhode, J. Acoust. Soc. Am. Suppl. 1 49, S1218 (1971)]. This review will briefly summarize the major findings of the early years as background to a presentation of several issues that are the focus of contemporary work. The steady-state and transient velocity responses of the basilar membrane characterize the capacity of the biological amplification mechanism in the organ of Corti and indicate that a ‘‘gain’’ of 40–60 dB is provided by the outer hair cells. Considerable response distortion accompanies this gain, and wave propagation of certain distortion products occurs. Electrical stimulation of the outer hair cells provides evidence of their mechanical role in the amplification mechanism by demonstration of the frequency range and displacement capacity of the cells. Efferent innervation of the organ of Corti is found to modulate the mechanical activity of the system.
Perception of amplitude fluctuation in the goldfish.
Authors: Chronopoulos M. , Fay R. , Dye R. , Sheft S. , Shofner W.
Published: October 2005

This experiment investigates the extent to which the goldfish’s response to amplitude-modulated and phase-manipulated sounds can be predicted by the power of envelope fluctuation. Sixteen common goldfish, Carassius auratus, were classically conditioned to suppress respiration to a 350-Hz carrier 100% sinusoidally amplitude modulated at 30 Hz. In a subsequently generalization test session, respiratory suppression was measured in the presence of novel signals having either sidebands attenuated or carrier phases shifted up to 90 °. Respiratory suppression declined with both increases in sideband attenuation and increases in phase shift of the carrier frequency. Respiratory responses to both sideband attenuated and phase-shifted signals declined along a single, monotonic function of envelope power as defined by the normalized fourth moment [W. Hartmann and J. Pumplin, J. Acoust. Soc. Am. 90, 1986–1999 (1991)]. The goldfish’s performance in this experiment is comparable to the performance of human listeners in experiments on roughness scaling [C. Mathes and L. Miller, J. Acoust. Soc. Am. 19, 780–797 (1947)]. [Work supported by a NIH, NIDCD Program Project Grant to the Parmly Hearing Institute.]
Perception of musical pitch with electrical stimulation of the cochlea.
Authors: McDermott Hugh J. , McKay Colette M.
Published: October 2005

For cochlear implant users to obtain enjoyment from music, it is essential that they be able to perceive melodic pitch. Previous studies have indicated that the ‘‘pitch’’ or timbre of pulsatile electrical stimuli varies with the repetition rate or intracochlear site of delivery, but generally pitch has been defined loosely as a tonal quality that can be ranked in terms of ‘‘sharpness.’’ In a recent series of experiments, a user of the Nucleus 22-electrode implant was asked to judge or adjust the musical interval between pairs of stimuli. The electrical parameters investigated included the frequency of sinusoidally amplitude-modulated pulse trains, as well as pulse rate and active electrode position. The subject was able to judge the pitches using only the interval names (‘‘fifth’’ ‘‘octave,’’ etc.), and without specific training, the guidance of familiar melodies, or rhythm cues. The results showed that rate or modulation frequency could convey musical pitch over a range of approximately two octaves, and followed a relationship comparable with that for acoustic stimuli and normal hearing. The pitch related to electrode position could also be labeled in musical terms. Interestingly, when both place and rate varied together, the pitch associated with electrode position was generally dominant.
Fluid-loaded plate coupled to a distributed inhomogeneity—Review.
Authors: Cuschieri Joseph. M. , Feit David
Published: October 2005

The problem of scattering from a fluid-loaded plate structure coupled to a distributed inhomogeneity is considered. Results have been presented which include the plate surface velocity Green’s function, the far-field and near-field scattered pressure, and the acoustic and structural intensity. The distributed inhomogeneities considered varied both in type (mass or stiffness) and shape. In all instances, the perturbation due to the inhomogeneity, relative to the elastic characteristics of the plate, is small. In the case of shape variations, the influence of ‘‘smoothness’’at the edges of the inhomogeneity, and of oscillations within the inhomogeneity distribution were also considered. In this presentation, the results that have been generated thus far, will be reviewed and general conclusions drawn from these results. It is shown that depending on the frequency range of interest, the results can be significantly influenced by the shape and type of inhomogeneity. Stiffness inhomogeneities, in general, are less significant compared to mass inhomogeneities. However, in relative terms, internal variations in the inhomogeneity shape are more significant for stiffness inhomogeneities than for mass inhomogeneities. Alternate forms of presenting the results will be explored. [Work sponsored by ONR.]
Stability of clamped rectangular plates in uniform subsonic flow.
Authors: Zhu Jinshuo , Wu Sean F.
Published: October 2005

This paper depicts the stability charts of rectangular plates clamped to an infinite, rigid baffle in uniform subsonic flow. The correlations among the critical flow speeds and the plate aspect ratio, plate thickness/length ratio, and plate/fluid density ratio are exhibited. Results show that when the flow speed exceeds a critical value, the plate may vibrate around an equilibrium position other than its undeformed one. When the flow speed exceeds all the critical values, the plate may be locally unstable at all equilibrium positions. In particular, it may jump from one equilibrium position to another in a random fashion. These local instabilities are controlled by structural nonlinearities. Without the inclusion of structural nonlinearities, the plate may have only one equilibrium position, namely, its undeformed one. The amplitude of plate vibration would then grow unboundedly when the flow speed exceeds the critical value, known as absolute instability. With the inclusion of structural nonlinearities, the plate may have more than one equilibrium position when the flow speed exceeds the critical values. Under this condition, plate vibration may seem chaotic, the overall amplitude of flexural vibration is nevertheless bounded.
Enhancement of the transmission loss of panel structures through the application of segmented, resonant foam attachments.
Authors: Bolton J. Stuart , Kang Yeon June
Published: October 2005

In noise control foam both the bulk solid and fluid phases participate significantly in the wave propagation process. Here it is suggested that resonances of the foam’s solid phase can be tuned to produce significant narrow-band absorption superimposed upon the broadband attenuation characteristic typically offered by the fluid phase of an elastic porous material. Two approaches have been considered. In the first, aluminum masses are applied to small pieces of foam (say, 25 mm square and 6 mm deep) that are then attached to a panel. Each piece of foam then comprises a small resonator whose natural frequency is essentially determined by the bulk stiffness of the solid phase of the foam together with the added mass. It has been found that the application of an array of foam resonators causes the transmission loss of the base panel to be increased over approximately an octave. In a second approach, a continuous foam lining is segmented, and a piece of perforated metal is applied to each segment. Again, a narrow-band increase in transmission loss is observed, in this case combined with the broadband transmission loss increase normally produced by a layer of porous material.
Spectral elements for acoustic wave propagation through thin-walled complex structures.
Authors: Bilodeau Brian A. , Doyle James F.
Published: October 2005

Noise generation is an aspect of structural impacts not receiving much attention. Reasons for this include the fact that the problem requires analyzing the solid/fluid interaction as well as the need to model extended regions. Spectral elements are developed for analyzing acoustic wave propagation through thin-walled structures. Both flat- and curved-plate elements, which incorporate the effect of fluid loading on the structure, are developed. These elements exactly model the responses over large domains and through their generalized nodes may be conveniently joined to model complex structures composed of many segments and faces. Results for the impact of flat and curved panel systems are presented. In addition, the utility of the spectral method for computing frequency response functions directly is demonstrated.
Spectral integral approach to radiation from fluid-filled boreholes.
Authors: Rao V. N. Rama , Schmidt Henrik , Vandiver J. Kim
Published: October 2005

A hybrid model for radiation from a borehole while drilling has been developed. A numerical model for propagation in a borehole including a drill pipe has been combined with the OASES frequency–wave-number model for propagation in layered earth media, using the concept of effective sources. Equivalent line source arrays that produce the same far-field radiation as the borehole are first computed. These are then introduced into the layered earth model and the resultant seismic wave field is computed. The borehole modes are excited by a displacement source at the bottom, simulating bit motion while drilling. In contrast to earlier work the present model includes the drill pipe in the simulation, allowing for three propagating modes at low frequencies. The model has been applied to analysis of the role of the formation composition in the radiation from the tube modes. The fundamental differences between the radiation into soft and hard formations are discussed and demonstrated, including the formation of Mach cones along the borehole in soft formations.

All posters will be on display from 8:30 to 11:30 a.m. To allow contributors an opportunity to see other posters, contributors of odd-numbered papers will be at their posters from 8:30 to 10:00 a.m. and contributors of even-numbered papers will be at their posters from 10:00 to 11:30 a.m.
The effects of center frequency and bandwidth on the discriminability of noise.
Authors: Rickert Martin E. , Robinson Donald E.
Published: October 2005

When listeners are asked to discriminate between trials on which a sample of noise is presented twice and trials on which two nonidentical samples are presented, discriminations are easier if samples differ near the end rather than near the beginning. The effect of temporal position [S. F. Coble and D. E. Robinson, J. Acoust. Soc. Am. 92, 2630–2635 (1992)] is robust over a wide range of stimulus parameters including duration, level, and correlation. In previously reported work [M. E. Rickert and D. E. Robinson, J. Acoust. Soc. Am. 98, 2906(A) (1995)], discriminability was measured with wideband (100–3000 Hz) and narrow-band (455–655 Hz) noise. The size of the effect of temporal position is smaller with the narrow-band noise. However, one could argue that these effects are restricted to the lower region of the frequency spectrum because center frequency was held constant (≊ 545 Hz). In the experiment reported here, both center frequency (545 and 2000 Hz) and bandwidth (200 and 1000 Hz) were investigated. Data were also obtained with wideband (100–3000 Hz) noise. Although the effect of temporal position is consistent across stimulus conditions, the size of the effect is reduced for narrower bandwidths. There is no evidence of an effect of center frequency. Results are discussed in terms of a leaky integrator model [D. E. Robinson and M. E. Rickert, J. Acoust. Soc. Am. 98, 2906(A) (1995)]. [Work supported by NIH and AFOSR.]
Peripheral origins of the upward spread of masking.
Authors: Oxenham Andrew J. , Plack Christopher J.
Published: October 2005

Recent physiological studies have shown that the basilar membrane (BM) response to tones at characteristic frequency (CF) is highly compressive at medium levels, with a ratio of about 5:1, while the response to tones well below CF is linear. A psychophysical measurement of these characteristics was attempted using forward masking, to avoid peripheral interaction of stimuli, with a 4-ms, 6-kHz signal presented 2 ms after the offset of a 100-ms, 3-kHz masker, in order to measure thresholds at high signal levels. The growth of masking was very compressive at medium signal levels; increasing the signal level from 50 to 70 dB SPL resulted in a mean increase in masker level of only 3.6 dB. Growth at lower and higher signal levels was more linear. Thresholds were also measured for a number of other masker frequencies. As expected, the difference between masker and signal growth rate decreased as the masker frequency approached signal frequency. The results are quantitatively consistent with the hypothesis that BM nonlinearity governs the upward spread of masking. Furthermore, the technique may provide a simple way of estimating BM nonlinearity in humans. [Supported by the Wellcome Trust and the Royal Society.]
Basilar membrane nonlinearity and the growth of forward masking.
Authors: Plack Christopher J. , Oxenham Andrew J.
Published: October 2005

Psychophysical forward masking generally grows nonlinearly, with a given increase in signal level requiring a larger increase in masker level for the signal to remain at threshold. In the present experiments, a 10-ms sinusoidal signal was presented 2 ms after a 20-ms sinusoidal masker at the same frequency. Frequencies of 2 and 6 kHz were tested. It was shown that, while the masker level needed grew faster than the signal level at low signal levels, at medium signal levels the reverse was the case. These results can be understood in terms of a basilar membrane response that is compressive at medium levels and more linear at low and high levels. When the masker is in the compressive region and the signal is in the lower, more linear, region, then large increases in masker level are needed for a small increase in signal level. When the signal is in the compressive region and the masker is in the higher, more linear, region, then large increases in signal level are needed for a small increase in masker level. [Work supported by the Royal Society and the Wellcome Trust.]
Psychophysical evidence of excitatory connections across auditory frequency channels.
Authors: Wright Beverly A.
Published: October 2005

A simultaneously masked auditory signal becomes easier to detect as its onset is delayed from masker onset. This ‘‘enhancement effect’’ depends upon masking components presented outside of the signal’s frequency channel, indicating the participation of an across-channel process. The nature of this process has not been clearly established due to the difficulty of separating the influence of excitation and inhibition in simultaneous masking. Here, the forward-masked threshold of a 20-ms, 1000-Hz tone was determined in the presence of one or two masking tones [M1 (1000 Hz, 50 dB) and M2 (variable from 500 to 3000 Hz, 70 dB)]. When the masker duration was 500 ms, adding M2 to M1 reduced signal threshold when M2 was presented at 1150 Hz (suppression), but had no influence on performance when M2 was above about 1300 Hz. In contrast, when the masker duration was 40 ms, adding M2 to M1 did not lower threshold at 1150 Hz, and always increased threshold when M2 was presented above 1300 Hz. This latter threshold increase was reduced when a third masking tone presented at 1150 Hz was added to M1 and M2. These results suggest that the across-channel process involved in the enhancement effect is excitatory, adapts, and is moderated by suppression. [Work supported by NIDCD.]
First circumferential wave in the low-frequency scattering by a viscoelastic cylinder.
Authors: Chati Farid , Leon Fernand , Maze Gérard
Published: October 2005

Acoustic scattering from an absorptive cylinder (Lucite) of infinite length excited by a normal plane acoustic wave is investigated in low frequencies. This one is assumed to be homogeneous and isotropic in its viscoelastic properties. The experimental results are obtained with a method of isolation and identification of resonances (MIIR). The resonance spectra are particularly studied. In the given frequency range, the presence of six families of circumferential waves labeled lw (1≤lw≤6) was noted. The resonances of these families, except lw=1, are wide compared to those of aluminum or steel cylinders. Nevertheless, the resonances of the first family are easily detected in the Lucite cylinder, contrary to aluminum or steel cylinders. The scattering of a plane-wave pulse can be represented by the Fourier integral in order to determine a theoretical resonance spectrum without choosing the background. A good agreement is obtained for the studied frequency range between experimental and theoretical results. In the case of aluminum or steel cylinders, the computed calculus in vacuum are in good agreement with the experimental results. In the case of the Lucite cylinder, that is not verified, particularly with the first family. Moreover, the effect of the external fluid density on the resonances is analyzed.
Backscattering due to ray reverberations between nonconcentric surfaces of a thick shell: Ray stability, transitions in wavefront shapes, and observed scattering enhancements due to focusing.
Authors: Morse Scot F. , Marston Philip L.
Published: October 2005

The paraxial ray stability analysis previously developed for laser resonators is applied to high-frequency elastic wave reverberations across the thickness of a shell having nonconcentric surfaces. A previous summation of backscattered amplitudes from rays reverberant within concentric surfaces [S. G. Kargl and P. L. Marston, J. Acoust. Soc. Am. 88, 1114–1122 (1990)] is found to lie on the boundary between stable and unstable resonators. Shifting the center of the inner surface of the shell away from the direction of the source produces a stable resonator. Rays reverberant between such nonconcentric surfaces produce a far-field focusing that is periodic in the number of internal bounces. Exact ray tracing, used to identify scattered wavefront shapes near focal conditions, reveals the presence of glory rays (off-axis rays which are exactly backscattered). Shifting the inner surface of the shell toward the source produces an unstable resonator and no focused rays. The existence of backscattering enhancements by focused reverberant rays for a stable resonator was confirmed with experimental observations with elastic scatterers in water having nonconcentric spherical surfaces. [Sponsored by the Office of Naval Research.]
Scattering by elastic elliptical cylinders of different aspect ratio.
Authors: Lanfranchi Jacques , Maze Gérard
Published: October 2005

The scattering of elliptical cylinders of infinite length insonified by an incident beam perpendicular to their axis is investigated. The method of isolation and identification of resonances (MIIR) allows one to plot resonance spectra. These spectra are obtained from three targets characterized by their major radius/minor radius ratio equal to 4/3, 4/2, 4/1. The resonance spectra obtained from a circular cylinder excited in the same conditions show peaks related to circumferential waves which, for particular frequencies, constitute standing waves. In this case, the phase velocity depends only on the frequency. Contrary to the circular cylinder, resonance spectra obtained by an experimental monostatic method depend on the azimuthal position of the transducer. Some resonances vanish at certain positions. In this case, the phase velocity and the coupling coefficient are a function of the curvature radius and the frequency. The wavelength is not identical on the circumference of the elliptical cylinder. To explain the experimental results, a phase-matching model is developed to determine the resonance frequencies [H. Überall et al., J. Acoust. Soc. Am. 81, 312–315 (1987)]. This method allows one to represent the vibration state on the circumference. An integral calculus applied on the latter result gives the far-field pressure.
Acoustical scattering by a density contrast wedge.
Authors: Davis Anthony M. J. , Scharstein Robert W.
Published: October 2005

Consider the three-dimensional scattering of a sound pulse generated by an impulsive point source and incident upon a penetrable wedge, identified by a density contrast. The wave speed is common to both regions and the radiation condition of only outgoing waves at infinity is applied in all directions. At the boundary of the wedge there is a pair of transmission conditions which ensure continuity of the acoustic pressure and normal velocity. By using Fourier transforms in time and parallel to the wedge generators and a Kontorovich–Lebedev transform in the radial direction, as described by Jones [Acoustic and Electromagnetic Waves, Oxford (1986)], both the exterior and interior fields can be obtained as a sum of impulsive terms, some of which are due to edge diffraction. If the wedge angle is a rational fraction of π, then the residue series can be summed and, after careful consideration of when and where impulsive disturbances can occur, the fields can be written in remarkably simple closed forms. This solution provides the zero-order field for a relatively small difference in wave speeds.
Articulatory model for female and child speakers.
Authors: Ananthapadmanabha T. V.
Published: October 2005

Articulatory models reported in the literature are generally meant for a prototype male speaker. One such popular model is that proposed by Mermelstein [J. Acoust. Soc. Am. 53, 1070–1083 (1973)]. In this paper the scope of Mermelstein’s model is extended to adopt it for any male speaker as well as for female and child speakers. The default vocal tract shape of the model for a given vowel is determined. The axis of the vocal tract is divided into a number of sections. Vocal tract length as well as section lengths are determined. To adopt the model for a male speaker with a vocal tract length different from that of the model, the section lengths are uniformly scaled. To adopt the model for a female or child speaker, the section lengths are scaled disproportionately over the pharyngeal and oral cavity to attain the speaker’s vocal tract length. The disproportionate scale factors are based on the anatomical data. Accuracy and application of the extended model are discussed.
Prosody as a potential cue for age perception.
Authors: Ralston James V. , Fidas George , Agli Christin E. , Coppola Colleen
Published: October 2005

Previous research has shown that relatively localized acoustic information, such as voice pitch, f0 perturbation, and hoarseness are cues to age perception. The present studies examined the potential role of sentence-level prosodic information in the perception of age. Sixteen different six-word sentences were recorded from eight different males in each of three age groups (middle school students, college students, and senior citizens). Several acoustic measurements were made of each sentence, including mean frequency, slope of intonation contour across entire sentence, slope of terminal fall, and amount of inflection (i.e., absolute frequency change summed across the sentence). A second set of sentences was constructed by randomly reordering the words in each sentence. Original sentences and their scrambled counterparts were presented to 19 listeners who rated the age in years of the speaker of each sentence. Analyses of variance revealed that age judgments were less extreme for scrambled sentences as compared to the regular sentences, particularly for the college-aged and elder voices. These results suggest that the scrambling altered sentence-level vocal information. Preliminary regression analyses also indicate that perceived age is related to some relatively global acoustic measures, such as amount of inflection.