bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of spectral contrast on perceptual compensation for spectral-envelope distortion
Authors: Watkins Anthony J. , Makin Simon J.
Published: October 2005

Features in a sound’s spectral envelope are important for perceptual identification but they are likely to be accompanied by spurious features due to distortion by the transmission channel between source and listener. Previous experiments have demonstrated that there is perceptual compensation for this distortion, and the present experiments ask whether the compensation involves a separation of spurious and salient features. Listeners identified words containing a vowel test sound in an /æpt/ to /■pt/ continuum, with a carrier phrase before each word. Effects of transmission channels were simulated by filtering the carrier and the /pt/ following the test sound. Filters were pairs with frequency responses that were the difference of the spectral envelopes from the end-point vowels. Contrasts were altered by multiplying decibel values of the carrier filter’s frequency response or the test sound’s spectral envelope by a positive number. This keeps features such as peaks at the same frequencies but changes the difference in level between peaks and valleys. When the contrasts of the carrier filters and test sound were the same, the continuum’s phoneme boundary was shifted in a manner consistent with a perceptual compensation for the filters that affects the neighboring test sound. However, this shift decreased when the carrier-filter’s contrast was less than that of the test sound, and increased slightly when the test-sound’s contrast was less than the carrier-filter’s contrast. Therefore, the amount of compensation increases with the amount of distortion, even when spectral features such as peaks are kept at the same frequencies. So compensation seems to occur before any perceptual extraction of these features.
The effect of turbulent intermittency on scattering into an acoustic shadow zone
Authors: Wilson D. Keith , Wyngaard John C. , Havelock David I.
Published: October 2005

Classical scattering theory predicts that the intensity of a saturated, scattered signal will have an exponential probability density function (pdf). However, the classical theory does not account for intermittency of the turbulence, which causes quantities such as the scattering cross section to vary in space and time. The classical theory can be modified to include intermittency by making the strength of the turbulence (i.e., the dissipation rate of turbulent kinetic energy) a local property of the scattering volume. The dissipation rate averaged over the scattering volume has a log-normal pdf. The intermittent theory is compared to measured pdf’s obtained for scattering into an outdoor, ground-based, acoustic shadow zone. Deviations from the exponential pdf are observed readily in the data, and are predicted well by the intermittent theory. Intermittency is shown to dramatically increase the probability of measuring large values of the scattered intensity.
Torsional vibration of coaxially segmented, tangentially polarized piezoelectric ceramic tubes
Authors: Shuyu Lin
Published: October 2005

Piezoelectric ceramic materials are often used in ultrasonic and underwater sound transducers by stacking a number of identical pieces together. In this paper, the theoretical behavior is derived for a piezoelectric ceramic cylindrical tube consisting of any number of tangentially polarized coaxial segments. The resonance frequency equation of the torsional tube is obtained and the electromechanical equivalent circuits are developed that greatly simplify and improve the analysis of composite resonators in transducer design. A new parameter which is defined as the cross-sectional torsional coefficient is presented. The relations between the theoretical parameters and the experimentally measured quantities of the segmented electromechanical system in torsional vibration are obtained so that the material parameters can be evaluated even though the lateral dimensions are large relative to the length of each individual segment and the analysis of the vibrational characteristics of the torsional transducer can be simplified.
Anisotropy of the transverse mode ultrasonic properties of fixed tendon and fixed myocardium
Authors: Hoffmeister Brent K. , Gehr Sara Elizabeth , Miller James G.
Published: October 2005

This study investigates the influence of the fiber-reinforced nature of myocardium and tendon on the propagation of transverse mode ultrasonic waves. Formalin fixed specimens of normal human left ventricular cardiac muscle and bovine Achilles tendon were prepared for this study in such a way that transverse mode ultrasonic waves could be propagated perpendicular to the fiber axis of the tissue with the polarization oriented either parallel or perpendicular to the fiber axis. Measurements of velocity and attenuation were made at 3 MHz to assess the degree of anisotropy in these parameters for both tissues. Formalin fixed tendon exhibited a significant anisotropy whereas formalin fixed myocardium displayed a similar trend of more modest magnitude. Results of these measurements were used to compute two elastic stiffness coefficients for each tissue, yielding c44=37.2 MPa and c66=18.0 MPa for formalin fixed tendon, and c44=8.97 MPa and c66=8.45 MPa for formalin fixed myocardium. To validate this approach, additional studies were conducted to measure the transverse mode ultrasonic properties of silicone rubber and motor oil.
Anisotropy of the slope of ultrasonic attenuation in formalin fixed human myocardium
Authors: Verdonk Edward D. , Hoffmeister Brent K. , Wickline Samuel A. , Miller James G.
Published: October 2005

Clinical implementation of quantitative ultrasonic tissue characterization is likely to require imaging the heart with sound propagating at varying angles relative to the fibers of the heart. Under these circumstances, the variation of the ultrasonic properties of myocardium with the angle of propagation relative to the myofibers may represent a significant source of potential misinterpretation. In the present study, the systematic approach of assessing the impact of anisotropy on quantitative myocardial tissue characterization is extended by reporting results of a recent in vitro study to measure the anisotropy of the slope of ultrasonic attenuation in specimens of formalin fixed human myocardium. Data obtained from regions of remote infarct are presented and compared to data acquired from regions identified to be free of infarct. The slope of attenuation for both regions exhibit a sinusoid-like dependence on angle that is approximately doubled for propagation parallel to the fibers as compared to perpendicular. These results are, in turn, compared to an earlier study from the laboratory that examined the effects of myocardial infarction on ultrasonic attenuation and interstitial collagen content in freshly excised canine hearts. Discussion regarding the analysis and interpretation of measurements of slope of attenuation is presented as well as a discussion of the possible influence of formalin fixation on our results.
Acoustic reflectivity of a dolphin
Authors: Au Whitlow W. L.
Published: October 2005

Backscatter measurements were made on a stationary Atlantic bottlenosed dolphin under controlled conditions. Three sets of measurements were made: (1) broadside aspect target strength as a function of frequency from 23 to 80 kHz; (2) relative target strength as a function of the polar angle about the animal using a short click signal having a peak frequency of 67 kHz; and (3) relative reflective strength of different portions of the animal’s body. The mean target strength at the broadside aspect decreased from −11 to −24 dB as the frequency increased from 23 to 45 kHz. As the frequency increased from 45 kHz, the target strength rose to a local maximum of −18 dB at 66 kHz and then decreased to −23 dB at 79 kHz. Maximum target strength was measured at the broadside aspect and exceeded the minimum (tail aspect) target strength by 21 dB. The target strength at the head aspect was 5 dB below that of the broadside aspect. Most acoustic energy was reflected from the area between the dorsal and pectoral fins, corresponding to the location of the dolphin’s lungs.
Pitch adaptive time-rate expansion for enhancing speech intelligibility
Authors: Wenndt Stanley J. , Burleigh Joan M. , Thompson Michael W.
Published: October 2005

Many factors can affect an individual’s ability to correctly discern speech signals. Among these factors are background noise and conflicting information signals. Some research studies have suggested that time-rate expansion of speech signals can result in increased intelligibility for certain population segments. However, little work has been done to quantify the effect of moderate levels of speech expansion under adverse listening conditions. This paper describes a pitch-adaptive implementation for generating high-quality, time-expanded speech. Clinical tests on 16 subjects using monosyllable words with additive noise show an overall improvement in intelligibility for the speech rates tested. The best results were achieved at an expansion rate of 30%, where the subjects showed an average improvement of 29.1% when compared with no time expansion.
Measurements with wire mesh stacks in thermoacoustic prime movers.
Authors: Hofler Thomas J. , Reed Mark S.
Published: October 2005

Measurements with various wire mesh ‘‘stacks’’ in two different thermoacoustic prime movers are presented. Stirling engine regenerators are commonly constructed by stacking disks cut from wire mesh (i.e., wire cloth or wire screen) in a tube. In addition to simplicity, this has two advantages for prime movers. First, the wire is relatively impervious to moderately high temperatures and second, the effective thermal conductivity of the structure is one to two orders of magnitude lower than a comparable metal ‘‘parallel plate’’ structure. Since no linear theoretical thermoacoustic models exist for these wire mesh stacks, this approach is simply to measure the performance of several different mesh stacks. Initial results indicate reasonably good onset temperature and amplitude performance. [Work supported by Office of Naval Research.]
Measurements of transient effects in thermoacoustics.
Authors: Jones Albert B. , Atchley Anthony A. , Hebert David D. , Lin Hsiao-Tseng , Meng Ching-Kai , Salindong Arthur R.
Published: October 2005

Most theories of thermoacoustic phenomena deal with steady-state quantities. However, recent work by Prosperetti and co-workers is capable of treating the transient part as well. Motivated by these predictions, measurements are presented of the evolution of the temperature distribution along a stack plate exposed to a large amplitude standing wave and the evolution of the pressure waveform within a prime mover. Qualitative measurements of the former and both qualitative and quantitative measurements of the latter have been reported by various authors previously. The purpose of the present series of measurements is to provide a more complete set of data to test theoretical predictions. [Work supported by the Office of Naval Research.]
The heat transfer coefficient between stack and heat exchanger as a function of thermal penetration depth.
Authors: Brewster James R. , Raspet Richard , Bass Henry E.
Published: October 2005

The heat transfer coefficient between two elements of a thermoacoustic device is defined as being the ratio between the rate of heat flow between them and the temperature difference occurring at the interface. Previous experiments have demonstrated that this quantity is proportional to the amplitude of acoustic oscillation. For stack and heat exchanger duct widths that are comparable to the thermal penetration depth, the heat transfer coefficient was found to be equal to that predicted by a theory based on the elements of the engine being perfect heat exchangers. Results of experimental measurements of the variation of heat transfer coefficient as a function of frequency will be presented. Increasing the frequency reduces the thermal penetration depth allowing the effects of partial thermal contact within the elements to be evaluated. These results will be compared to attempts to build theoretical models of the heat exchange process.
Understanding the periodic driving pressure in the Rayleigh–Plesset equation.
Authors: Moss William C.
Published: October 2005

The radial motion of a single bubble in a periodically driven liquid is simulated by solving the Rayleigh–Plesset equation and the fully compressible hydrodynamic equations. The hydrodynamic equations require a much smaller far-field periodic driving pressure than the Rayleigh-Plesset equations to produce the same maximum bubble radius. The discrepancy is resolved by constructing analytic traveling and standing wave solutions that show the relationship between the far-field periodic driving pressure and the pressure near the bubble, which is actually responsible for the radial motion. [This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.]
Intensified cavitation produced with pressure release and rigid ellipsoidal reflectors.
Authors: Bailey Michael R. , Blackstock David T.
Published: October 2005

An underwater bubble is well known to grow in response to a strong negative acoustic pulse and then collapse because of inertial forces. Here it is shown that adding an auxiliary positive pulse after collapse begins intensifies the collapse. The negative-then-positive pulse sequence is produced by two ellipsoidal reflectors, each with an electrical spark at its near focus f1 and beamed so that they share a common second focus f2. The negative pulse is produced by a polyurethane (pressure release) ellipsoid, the positive by a brass (rigid) ellipsoid. A timing circuit controls the delay between the pulses. Cavitation is recorded by pitting (caused by bubble collapse) of an aluminum foil membrane, which is centered at f2 and lies coplanar with the two crossed beams. When the brass reflector is fired alone, a narrow path of ∼1-mm diameter pits appears. Firing the polyurethane reflector alone yields more widespread, ∼0.1-mm diameter pits. When both are fired, a pitted X pattern shows the position of the two beams. If the delay between the two firings is 2–6 μs, the intersection of and the centerline between the paths erupts with deep pits. [Work supported by ONR.]
Effect of probe frequency on the click-rate-induced facilitation of the acoustic reflex thresholds.
Authors: Rawool Vishakha W.
Published: October 2005

Ipsilateral click thresholds obtained with a 226-Hz probe tone can improve by approximately 21 dB, with an increase in the click repetition rates from 50/s to 300/s [Rawool, Scand. Audiol. 24, 199–205 (1995)]. This investigation was designed to evaluate the effect of higher probe frequencies on the click-evoked acoustic reflex thresholds and on the rate-induced improvement in the acoustic reflex thresholds. Twelve female and six male subjects with normal hearing participated in the study. Ipsilateral acoustic reflex thresholds were obtained from the left ear of each subject by presenting clicks at the repetition rates of 60, 120, 180, 240, and 300 clicks/s. The results were obtained for three probe tone frequencies: 226, 678, and 1000 Hz. All the subjects showed a decrease in admittance for the 226-Hz probe and an increase in the admittance for the 1000-Hz probe. For the 678-Hz probe, some subjects showed an increase in admittance and others showed a decrease in admittance. The acoustic reflex thresholds were significantly elevated for the 678-Hz probe tone. The rate-induced improvement in acoustic reflex thresholds for each subject was calculated as the difference between the minimum and maximum acoustic reflex thresholds. This improvement (13 to 17 dB) was not significantly different for the three probe tones.
Middle ear of a lion: Comparison of structure and function to domestic cat.
Authors: Huang Gregory T. , Rosowski John J. , Flandermeyer Deborah T. , Peake William T.
Published: October 2005

Acoustic and anatomical measurements have been made in a deceased lion (Panthera leo) and compared to measurements in domestic cat (Felis catus). The results are used to test a model in which the acoustic impedance at the tympanic membrane (TM) is the sum of (1) the impedance of the TM and ossicular chain and (2) the impedance of the middle-ear cavities. Impedance was measured at the TM in lion before and after manipulation of the cavity structures; sound pressure in the cavities was measured simultaneously. CT sections of the lion middle ear were used to reconstruct the tympanic ring, the tympanic cavity, the bullar cavity, and the foramen that connects these cavities. A quantitative comparison of these structures shows that ear dimensions in the lion are roughly two times those in cats. Acoustic measurements in the lion and cat are qualitatively similar, but the lion middle-ear impedance is generally smaller. A six-element analog circuit model captures the main features of both sets of measurements. The acoustic effects of the size differences are represented by changes in the circuit model element values. In its ear, the lion is just a big pussycat. [Work supported by NIDCD.]
On the relation of distortion product and transient evoked emission spectral fine structure.
Authors: Uppenkamp Stefan , Mauermann Manfred , Kollmeier Birger
Published: October 2005

Both distortion product emissions and transiently evoked emissions typically exhibit an individual fine structure, which seems to be linked to the fine structure of threshold in quiet observable in many normal hearing subjects. However, the recording paradigm for both experiments is rather different. Narrow-band distortion product emissions are detectable during continuous stimulation with two sinusoids. They represent the nonlinear interaction of the two tones in a stationary condition. Transient evoked emissions on the other hand may be interpreted as a type of impulse response of a nonlinear system. The frequency specificity is comparatively low. The interrelation of both types of emissions is not completely understood until now. To test the hypothesis of a common origin, patterns of spectral fine structure of DPOAE and TEOAE results from normal hearing subjects are compared. In addition, the influence of suppressor tones is investigated in both experiments. Results will be discussed in connection to current ideas about wave-fixed and place-fixed generation of emissions along the cochlear partition.
The development of forward masking in human infants.
Authors: Werner Lynne A.
Published: October 2005

It has been previously reported that 3-month-old human infants are more susceptible to forward masking than are adults of the same species. The purpose of the present study was to determine whether susceptibility to forward masking declines between 3 and 6 months of age. Six-month-old infants were trained to respond when they heard a train of alternating bursts of a broadband noise and a 1-kHz tone, but not when they heard the noise bursts alone. The tone burst had 16-ms rise and fall times and no steady-state duration. The interval between noise offset and tone onset, Δt, was either 10, 25, or 200 ms; Δt was fixed for each infant. The onset to onset interval between noise bursts was constant at 350 ms + Δt on all trials. The level of the noise was 65 dB SPL; its duration was 100 ms. The level of the tone was manipulated to define masked threshold. Six-month-olds demonstrated about 10 dB more forward masking than adults and about 10 dB less forward masking than 3-month-olds for short Δt, and about the same amount of masking as 3-month-olds for 200 ms Δt. [Work supported by NIH.]
Role of fundamental frequency differences in perception of simultaneous vowels by hearing-impaired listeners.
Authors: Arehart Kathryn Hoberg , King Catherine Arriaga , McLean Kelly S.
Published: October 2005

This study investigated the ability of normal-hearing listeners and listeners with moderate to moderately severe sensorineural hearing loss to use differences in fundamental frequency (F0) in the identification of monotically presented simultaneous vowels. Two psychophysical procedures, masked vowel identification and double-vowel identification, were used to measure identification performance as a function of F0 differences (0 through 12 semitones) between simultaneous vowels. The masked vowel identification task yielded thresholds representing signal-to-noise ratios at which listeners could just identify target vowels in the presence of a masking vowel. Performance in the double-vowel identification task was measured by the percentage of trials in which listeners correctly identified both vowels in a double vowel. As previously reported, normal-hearing listeners showed a sharp increase in the ability to separate simultaneous vowels as F0 differences increased from 0 to 1 semitone. Hearing-impaired listeners were less effective in using F0 differences in the perception of simultaneous vowels. Reasons for hearing-impaired listeners’ reduced performance probably include differences in their ability to use spectral and temporal cues across different frequency regions in their perception of complex-tone pitch. [Work supported by Deafness Research Foundation.]
Acoustic properties of the chinchilla pinna and ear canal.
Authors: Murphy William J. , Davis Rickie R.
Published: October 2005

Measurements of the acoustic transfer function (ATF) of the pinnae of 4 chinchillas were compared with the auditory-evoked potential (AEP) hearing thresholds of 16 chinchillas measured in free field and with insert earphones. The ATF was measured in anesthetized chinchillas in a far-field condition in a semi-anechoic room. Probe microphone measurements were collected just outside the pinna and at the tympanic membrane. The ATF exhibited a broad resonance between 2 and 6 kHz with about a 10 dB gain. The chinchillas were monauralized and had a chronic electrode implanted in the left inferior colliculus. The animals were awake and restrained during the AEP testing. The AEP measurements were averaged from 512 presentations of a toneburst at 0.5, 1, 2, 4, and 8 kHz. AEPs collected with insert earphones were calibrated with a probe microphone positioned near the tympanic membrane. The differences in the AEP hearing thresholds measured in the different configurations exhibited a 10 dB resonance at 4 kHz. The agreement between the ATF and AEP-derived transfer function suggested that the threshold differences from the two testing configurations could be accounted for by the pinna and ear canal gain.
Hearing and development impairment in Down-syndrome children.
Authors: Feitosa M. Angela G. , Tristao Rosana M.
Published: October 2005

A growing number of studies have shown that Down-syndrome persons have a high incidence of auditory deficit and slow language development. Down-syndrome children were investigated with respect to (a) hearing level, (b) language development, (c) global development, and (d) environmental interaction. Fifty-one children, 6-47 months old, were observed, 22 of whom had Down syndrome. Controls included 13 children without diagnosis of mental impairment, and 16 children with mental impairment due to etiologies other than Down syndrome. None of the subjects had a previous diagnosis of hearing loss. Relations among levels of hearing, global and language development, home stimulation, and risk factors for hearing loss were analyzed. The Down-syndrome group showed significantly elevated auditory thresholds and a larger number of pathological findings in the external and middle ears, as compared to other groups. It also showed lower levels in language development, as compared to global development; and shortened latencies of waves I and V in BERA. [Work supported by CNPq and CORDE.]
Detection of frequency-modulated signals by cochlear-implant users.
Authors: Bicknell Ina Rea , Feth Lawrence L.
Published: October 2005

Many cochlear-implant users show postoperative improvement in the ability to hear speech but most rely on lip-reading to understand speech. To determine if this limitation on speech perception relates to impaired temporal resolution, and, thus, an inability to track rapid frequency changes which are characteristic of speech, temporal resolution thresholds (TRT) of adult implant users were determined by measuring their ability to discriminate between a glide signal, a sinusoid linearly modulated in frequency and a step signal, a sinusoid traversing the same frequency range but in two to five discrete steps. Performance of implanted subjects was extremely variable, but, generally, their TRTs were higher than those of age- and sex-matched normal-hearing controls. At certain frequencies and sweep extents, no implanted subjects were able to distinguish between step and glide signals of duration shorter than 300 ms. When the signal step number was no greater than two, one subject, using a Spectra speech processor, had TRTs near the 10 ms upper limit of the control TRTs. Extended frequency sweeps of 1350–1500 Hz with center frequencies of 3300–3400 Hz resulted in nearly normal TRTs for two of the implant users. [Work supported by the Dayton, OH VAMC and a grant from AFOSR.]
Auditory brain-stem responses in adults with chronic conductive hearing loss.
Authors: Ferguson Michael O. , Cook Raymond D. , Hall Joseph W. , Grose John H. , Pillsbury Harold C.
Published: October 2005

The ABR is a brief latency, electrophysiologic response that reflects synchronous neuronal activity from the auditory-nerve and brain-stem structures. Investigations have shown that children with early conductive impairment exhibit abnormalities in their ABR, suggesting that the nervous system has an element of plasticity during critical periods of development. However, no similar research has been undertaken on adults to determine whether ABR abnormalities associated with chronic conductive impairment also exist in this population. This study addresses that question by investigating the ABR in a group of adults with chronic conductive loss and a control group of normal-hearing adults. The goal was to determine whether chronic conductive hearing loss in adults would result in similar abnormal ABR measurements as seen in the juvenile population. Subjects were evaluated by comparing ABR interpeak latencies between waves I and III and waves I and V. In addition, interaural latency differences were assessed in cases of unilateral disease. Preliminary results suggest that ABR abnormalities associated with conductive impairment are present. Specifically, in the cases of unilateral disease,there is a significant difference between ears in the waves I–V interpeak latency which is independent of audiometric asymmetry. These data may indicate that an element of plasticity exists in the mature auditory system. [Work supported by NIH NIDCD.]
Intrinsic envelope fluctuations and modulation-detection thresholds for narrow-band noise carriers.
Authors: Dau Torsten , Verhey Jesko , Kohlrausch Armin
Published: October 2005

This contribution summarizes analytical properties of envelope modulation spectra of bandpass noise signals, which are relevant for the dependence of amplitude-modulation thresholds on modulation rate and noise carrier bandwidth. Lawson and Uhlenbeck [Threshold Signals (McGraw-Hill, New York)] showed in 1950 that the modulation spectrum, i.e., the power spectrum of the linear envelope of a bandpass noise, has an approximately triangular continuous spectrum besides the dc peak. For a constant overall level of a noise band, the total power of intrinsic noise fluctuations, i.e., the total area under the triangle, remains constant. The modulation spectrum, however, becomes broader with increasing noise bandwidth. For low modulation rates, this leads to a reduction in intrinsic modulation power. For higher modulation rates, the intrinsic modulation power increases. Simple analytical calculations are presented which compute the integrated modulation power of the noise within the transfer function of a hypothetical modulation filter. For a set of carrier bandwidths between 1 and 6000 Hz and for signal modulation of 5, 25, and 100 Hz the calculated values of overall modulation power are compared with experimentally obtained modulation detection thresholds, and with results from simulations of an auditory model.
A quantitative prediction of modulation masking with an optimal-detector model.
Authors: Dau Torsten , Kollmeier Birger , Kohlrausch Armin
Published: October 2005

A multichannel model is discussed which describes effects of spectral and temporal integration in amplitude-modulation detection and masking. Envelope fluctuations within each auditory channel are analyzed with a modulation filterbank. The parameters of the filterbank are the same for all auditory filters and were adjusted to allow the model to account for modulation detection and modulation masking data with narrow-band carriers at a high center frequency. In the detection stage, the outputs of all modulation filters from all excited peripheral channels are combined linearly with optimal weights. To integrate information across time, a ‘‘multiple-look’’ strategy is implemented within the detection stage. Model predictions are compared with literature data from Houtgast [J. Acoust. Soc. Am. 85, 1676–1680 (1989)]. The following three conditions were reproduced with a deviation of less than 3 dB between experiment and simulation. (1) Masking of test modulations in the range 2 to 64 Hz by a narrow-band masker modulation at 4, 8, or 16 Hz. (2) Modulation masking as a function of the masker-modulation level. (3) Modulation masking as a function of the masker-modulation bandwidth. The results from the simulations further support the hypothesis that amplitude fluctuations are processed by modulation-frequency-selective channels.
Distinctiveness and serial position effects in tonal sequences: Combining DDT and PTD.
Authors: Surprenant Aimee M.
Published: October 2005

The proportion-of-the-total duration rule (PTD) [Kidd and Watson, J. Acoust. Soc. Am. 92, 3109–3118 (1992)] states that the detectability of a change in a component of a tonal sequence can be predicted by the duration of the changed component relative to the sequence as a whole. A similar idea has been used in dimensional distinctiveness theory (DDT) [Neath, Mem. Cognit. 21, 689-698 (1993)] to account for primacy, recency, and other serial position effects in memory. An item will be remembered if it is more distinct along some dimension relative to possible competitors. These experiments explore the relation between DDT and PTD by examining the effect of inter-stimulus interval (ISI) on the detection of a change in one tone of a tonal sequence for each serial position in the sequence. Results show that, with increasing ISI, performance on the first items increases whereas performance on the final items decreases, as predicted by DDT. In addition, the interaction of PTD and ISI was explored for each serial position. This research combines theories proposed in the psychophysical and memory areas and suggests that a comprehensive principle based on relative distinctiveness can account for both perceptual and memory effects.
Within and across channel processes contributing to comodulation detection differences.
Authors: Borrill Stephen J. , Moore Brian C. J.
Published: October 2005

The threshold for detection of a narrow-band noise signal was determined in the presence of a masker consisting of two synchronously gated 20-Hz-wide bands of noise with a spectrum level of 65 dB which were comodulated. The maskers were spaced by ΔF Hz above and below the signal frequency (1500 Hz). A low-pass noise was used to mask any combination products. Three conditions were tested: signal and masker envelopes correlated (C), signal and masker envelopes uncorrelated (U), or sinusoidal signal of the same overall level (S). ΔF ranged from 200 to 1400 Hz. Masked thresholds for the U and S conditions were essentially identical for all ΔF. Thresholds were higher in the C condition, thus showing a comodulation detection difference (CDD). The CDD was greatest for ΔF between 400 and 600 Hz. A second set of conditions was used in which either one, both, or none of the masking bands was comodulated with the signal. This was done for three different masker spectrum levels at a ΔF of 600 Hz. The results suggest that the CDD seen in the first experiment was mainly due to the upward spread of masking from the lower band and not to an across-channel grouping effect.
Detection of tones in modulated noise: Effects of masker level and masker depth.
Authors: Bacon Sid P. , Lee Jungmee , Peterson Daniel N. , Rainey Dawne
Published: October 2005

It is possible to estimate temporal resolution at discrete spectral locations by subtracting the masked threshold produced by a modulated masker from that produced by an unmodulated masker (the difference is referred to as the modulated-unmodulated difference, or MUD). This paradigm may be especially useful for measuring temporal resolution in subjects with hearing loss, provided that the MUD is independent of level. The purpose of the present study was to examine the MUD as a function of masker level at several signal frequencies. In the first experiment, the sinusoidally amplitude-modulated masker had a depth (m) of 1.0. The MUD increased by as much as 15 dB as the spectrum level of the masker increased from 0 to 40 dB SPL. In the second experiment, the modulated masker had a depth of 0.75 or 1.0. When the masker depth was 1.0, the MUD increased with increasing masker level, as in experiment one. When it was 0.75, however, the MUD — though reduced — was essentially independent of masker level. These results suggest that a masker depth of 0.75 may be used to compare temporal resolution between normal-hearing and hearing-impaired subjects without being complicated by effects of masker level. [Work supported by NIDCD.]
E. J. Richards and jet noise research at Southampton 1951–56.
Authors: Powell Alan
Published: October 2005

Elfyn Richards became the first Professor of Aeronautical Engineering at University College, Southampton, in September 1950 and he immediately began planning for jet noise research. The author joined him in January 1951, remaining until August 1956. Some events of that period are reviewed. With Richards’ boundless energy and infectious enthusiasm, his indispensible help with more than a touch of impatience—kindly toward the author, less so for administrative barriers—progress was remarkably rapid, though the experimental apparati were in most respects very modest by later standards. The eighth power law for turbulent jet noise power (and the awkward lack of proportionality of peak frequency with velocity), the screech of choked jets and supersonic edgetones were all discovered in the first year. Feedback theories for the latter two, pulse jet noise, and other investigations such as shock wave interaction and means of reducing screech were soon to follow. Acoustically inducted fatigue (AIF) of aircraft structures caused by jet noise was predicted and soon after was found to occur in practice. Richards played some role in all of these topics, but his innumerable ideas and widening noise interests could not possibly all be addressed in that period.
Recalling some contributions by Elfyn Richards.
Authors: Dunn Stanley E.
Published: October 2005

Professor Elfyn Richards enjoyed a long and unusually notable career which ranged over engineering, education, and public policy development. The scope of his impact was international and, as the Honorary Fellow award by the Society proclaims, of particular importance in the United States. Toward the end of his career he made himself available to work with the Ocean Engineering Department at Florida Atlantic University. That interaction was to have a profound impact on the program and its subsequent success in a number of areas. This paper shares the highlights of Professor Richards’ collaboration with the department and discusses the benefits which were so dependent on the unique qualities of his character.
Structural damping by granular materials.
Authors: Lenzi Arcanjo
Published: October 2005

Studies on a useful and rarely used damping technique, the filling of cavity components with granular materials, are presented. Experimental studies show regions of maximum damping caused by standing wave formation in the material. The first maximum occurs when the internal dimension of the cavity is equal to one quarter of the longitudinal wavelength. The tuning of optimum damping to any desirable frequency requires accurate knowledge of the wave speed. Experiments show that wave speeds decrease with amplitude when strains reach values higher than about 10−6. This is caused by gross slip taking place at contacts which breaks the main structure of grain–grain contacts responsible for the propagation of elastic waves. Waves speed whose amplitude produce strain smaller than 10−6 were observed being independent of amplitude. Loss factors of granular materials also present identical variation with strain. At large strains (≳10−6) energy is mainly dissipated at grain contacts, by dry friction in partial and gross slip forms. For low strains, energy is dissipated by hysteresis inside the grains themselves. Applications of this technique to heavy structures are useful.
Experimental statistical energy analysis: A tool for the reduction of machinery noise.
Authors: Lalor N.
Published: October 2005

The use of statistical energy analysis (SEA) for the solution of vibroacoustic problems that occur with the operation of machinery, has only recently become practicable. This paper charts the developments that led from the early ideas of energy accountancy (EA) to the current SEA modeling techniques. The basic concept of EA, which was conceived to show the influence of the overall design parameters on the radiated noise, is explained and its limitations discussed. The paper then goes on to describe how the various practical difficulties preventing the application of SEA were overcome to the point where it could be used as a practical tool. Finally, a case history is presented in which an experimental SEA model is used to determine input (exciting) powers, power flow and sensitivity of the noise to parameter changes. In addition, the use of an optimization algorithm for driving the noise level down to a target spectrum within parameter and weight constraints is also demonstrated.
Professor Richards after his second retirement.
Authors: Cuschieri Joseph. M.
Published: October 2005

Professor Richards, or Prof, as he liked to be called, had just come back from Loughborough University, where he was the Vice-Chancellor. This was his second retirement. While searching for an appropriate research area, he identified machinery noise as an important issue. He formed the machinery noise group in 1975, which I joined in 1980. At the time the group had seven members. The main emphasis of the work was in the prediction and control of noise from impact machines—punch presses, drop hammers, etc. Prof wanted to take a new look at the parameters that control impact noise. A major contribution was the energy accountancy concept. Prof was a constant source of new and fresh ideas, he would question any result or conclusion, and always contributed new insight to the problem and the results. Prof certainly had a unique approach to get to the root of an issue. I was fortunate that I kept in contact with Prof after I came to the US, as a fresh Ph.D., to join the faculty at Florida Atlantic University. His enthusiasm, inquisitiveness, and broad experience were invaluable and had a significant influence on my career and I am sure that of others.
Pediatric cochlear implantation: A review.
Authors: Miyamoto Richard T.
Published: October 2005

The field of pediatric cochlear implantation has changed tremendously since the early 1980s when single-channel cochlear implants were first provided to postlingually deafened children in the United States. Although implantation in children was at first restricted to older children with postlingually acquired hearing loss, it is now common for prelingually deafened children as young as two years of age to receive a cochlear implant. Furthermore, the introduction of multichannel cochlear implants and improved signal processing strategies have resulted in far greater speech perception benefits than originally thought possible. This presentation will review the major developments in pediatric implantation and summarize the results to date. [Work supported by NIDCD Grant Nos. DC00064 and DC00423.]
Long-term performance of prelinguistically deaf children using the Nucleus 22 channel cochlear implant.
Authors: Staller Steven J. , Beiter Anne L.
Published: October 2005

A sample of 178 children have been followed annually for the past five years, to assess the development of speech perception abilities in early deafened children using a multichannel cochlear implant. A subset of these children who acquired deafness prior to the acquisition of language (prelinguistic) have shown continued improvement on a hierarchy of pediatric speech perception tests throughout the follow-up period. Implantation at an early age appears to improve the prognosis for development of more difficult speech perception skills. In addition, there appears to be a positive relationship between the emphasis on oral listening skills and the rate of acquisition of speech perception abilities. Throughout the duration of the longitudinal study, several new speech processing strategies have been introduced for the Nucleus implant system. The most recent (SPEAK) is an adaptive strategy that varies the rate of stimulation and the number of electrode is stimulated according to the frequency characteristics of the speech signal. SPEAK attempts to represent the dynamic nature of speech and provides improved spectral detail by virtue of 22 closely spaced electrodes. A sample of 34 prelinguistically deafened children demonstrated significant improvements in speech perception within six months of conversion to the new processing strategy.
Clinical investigation of the CLARION cochlear implant in children.
Authors: Osberger Mary Joe , Zimmerman-Phillips Sue , Soli Sigfrid
Published: October 2005

This presentation will summarize the design of the CLARION pediatric clinical trial and present initial findings on the subjects’ performance with the device. A repeated measures design is used to compare each subject’s preoperative performance with hearing aids to their postoperative implant performance on a battery of outcome measures. Six categories of audiologic outcome measures are administered to the subjects to achieve study end points that reflect the range of benefit predicted to occur in pediatric implant users over time. Postoperative evaluations with the CLARION are performed at 3, 6, and 12 months following initial stimulation, and semiannually thereafter. Initial findings comparing subjects’ preoperative performance to their 3-month postoperative performance with the CLARION reveal improvements on all speech perception outcome measures. Performance on the outcome measures, however, is confounded by the limited cognitive and linguistic skills of some of the subjects, especially in the youngest (2- and 3-year-old) children. Information will be presented on issues inherent in the design and implementation of a large multicenter study of this nature.
Speech production and language development in pediatric cochlear implant users.
Authors: Svirsky Mario A.
Published: October 2005

Cochlear implantation has been very successful in postlingually deafened children. Implants provide them with substantial levels of speech reception, which in turn allows them to achieve better intelligibility, speech production, and English language proficiency. Congenitally or prelingually deafened children, while less successful than the aforementioned group, have also shown benefit in speech production and language measures. Performance varies greatly in this group, but there appears to be a trend towards better results when implantation is performed earlier in life. This presentation will analyze measures of speech production and language ability in children deafened before age 3 (who comprise the vast majority of pediatric cochlear implant candidates) as well as in children who are later deafened. Individual and group data will be discussed in view of the subjects’ communication mode (oral or total communication), age at deafening, age at implant, and years of experience with the implant. [Work supported by NIDCD Grant Nos. DC00064 and DC00423.]
Speech production and use of sign by young cochlear implant users.
Authors: Tye-Murray Nancy , Spencer Linda , Tomblin Bruce
Published: October 2005

The use of sign and the emergence of speech skills by children who are deaf and use a cochlear implant were examined. Twenty-five children who had an average of 43 months of experience with a Nucleus cochlear implant and who are educated in a simultaneous communication environment engaged in spontaneous conversation and completed speech production and audiological tests. During spontaneous conversation, the children used voice and sign to express whole words in their conversations 70% of the time, voice only 21%, and sign only 9% of the time, suggesting that use of a cochlear implant does not result in elimination of signing. Children demonstrated a wide range of intelligibility. Pearson correlations indicated that children who had better intelligibility were most likely to use voice only, while children who had poor intelligibility were most likely to use sign only. Analysis of the children’s consonant production over time suggested that fricative production emerges relatively early; but follows emergence of other speech skills, including the ability to produce nasal consonants. Measures of consonant production were significantly correlated with measures of consonant perception. This suggests a close link between children’s ability to produce speech and perceive speech.
Acoustic characteristics of speech in French children using multichannel cochlear implants.
Authors: Tobey Emily A. , Uziel Alain , Sillon Martine , Vieu Adrienne , Artieres-Reuillard Francoise
Published: October 2005

Acoustic characteristics of speech production produced with and without auditory feedback from a multichannel cochlear implant was examined in eleven French speaking children with profound hearing losses. Subjects produced five repetitions of stimuli designed to contrast voice-onset times and vowel formant frequencies. Samples were collected with the implant turned on and after a 10-min period of the implant turned off. Stimuli were audio recorded, low-pass filtered, and digitized at a 10-kHz rate. VOT’s and formant frequencies were measured using Cspeech software. VOTs for the bilabial cognates, /b/ and /p/, revealed considerable overlap in temporal values when no auditory feedback was available. During conditions providing auditory feedback, VOTs shifted to more nearly normal values with minimal overlap. Vowel formant frequencies also shifted as a function of implant status; however, the patterns of shift differed across subjects and across feedback conditions. Data suggest pediatric users of cochlear implants are able to use auditory feedback to adjust their speech production; however, the relationships between auditory conditions and speech acoustics appear complex. [Work supported by the Ministere de la Sante and a visiting research scholar award from the University of Montpellier.]