bluuebunny/crossref_metadata_2025 huggingface dataset:
Contrast agent-induced cardiac arrhythmias in rats: Lesions and mechanisms of injury
Authors: Zachary James F. , Hartleben Sarah A. , Frizzell Leon A. , O’Brien William D.
Published: February 2014

Other than minor contraindications, no known meaningful health risks have been reported during the use of microbubble ultrasound echogenic contrast imaging agents in the United States. At this meeting, we have reported on electrocardiogram conduction abnormalities in rat hearts exposed to pulsed ultrasound following intravenous injection of a contrast agent. Rats had no meaningful conduction abnormalities when exposed to ultrasound alone or contrast agent alone but developed premature atrial and ventricular complexes and polymorphic ventricular tachycardia when a contrast agent was administered and the heart was exposed to pulsed ultrasound. When ultrasound exposure was concluded, cardiac arrhythmias ceased but reoccurred when ultrasound exposure was resumed. Acute multifocal coagulative necrosis of cardiac rhabdomyocytes was observed microscopically in myocardium of rats exposed to ultrasound following injection of a contrast agent. Because cardiac arrhythmias were induced only when a contrast agent interacted with ultrasound during exposure, the presence of myocardial lesions alone did not appear sufficient to serve as foci for ectopic electrical activity. These results suggest that a microbubble contrast agent through its biomechanical interactions with pulsed ultrasound has the potential to induce conduction abnormalities leading to potentially hazardous cardiac arrhythmias. [Work supported by NIH Grant No. HL58218.]
Ultrasound enhanced bone formation during mandibular osteodistraction in rabbits
Authors: El-Bialy Tarek H. , Magin Richard L. , Evans Carla A. , Zaki A. Moneim , Frizzell Leon A. , Royston Thomas J.
Published: February 2014

Distraction osteogenesis is used in orthopedics to lengthen bones, by cutting or breaking the bone and gradually separating the two pieces as new bone fills the intervening space. This study evaluated whether pulsed ultrasound can be used to shorten the long post-distraction period associated with mandibular osteodistraction. Twenty-one rabbits were divided into three groups of seven. The distraction started 72 h after surgically severing both sides of the mandible at a rate of 3 mm/day. Group 1 received ultrasound for 20 min on both sides of the mandible every other day (alternating sides). Group 2 received ultrasound on one side of the mandible every day for 20 min. Group 3 did not receive any ultrasound. Bone formation at the distraction site was assessed by in vivo photodensitometry on head radiographs, an in vivo (nondestructive) vibratory coherence test across the distraction site, a post-mortem, ex vivo (destructive) three-point bending mechanical test, and by post-mortem, ex vivo (destructive) histological examination. Statistical analyses performed using analysis of variance (ANVOVA) tests revealed that ultrasound enhanced bone formation at the distraction site as evidenced by the increase in new bone photodensity, mechanical properties, and histological maturation, especially when ultrasound was applied daily.
High-intensity focused ultrasound for noninvasive disease treatment: Theoretical predictions and experimental results
Authors: Curra Francesco P. , Kargl Steven G. , Lafon Cyril , Crum Lawrence A.
Published: February 2014

High-intensity focused ultrasound (HIFU) is becoming a widely accepted and ‘‘clean’’ modality to induce noninvasive coagulative necrosis of biological tissue for both cancer treatment and hemostasis. Theoretical predictions via the medusa (medical ultrasound algorithm) computer model of ultrasonic fields, temperature responses, and lesion dynamics are simulated for turkey breast. The model accounts for nonlinear sound propagation in inhomogeneous media, arbitrary frequency power law for acoustic attenuation, and temperature and lesion time histories. Generation of gas bubbles within the tissue may also be considered. Results are presented in terms of a comparison study with in vitro experiments on common turkey breast. Attention is mainly focused on temperature and lesion evolutions; in particular, induced lesion boundaries and collateral damage to surrounding areas.
Magnetostrictive hybrid transducers
Authors: Hughes W. Jack
Published: February 2014

The current need in many sonar systems is for a high-power broad-bandwidth projector with a relatively flat response. One of the prime candidates to accomplish this is a hybrid transducer that uses both a piezoelectric and magnetostrictive motor section connected mechanically in series in a tonpilz (longitudinal vibrator) configuration. This transducer has a double resonance separated by about one octave. The inherent shape of the transmit frequency responses dictate using the magnetostrictive section for the lower resonance, and the ceramic section for the upper resonance, including maintaining a high response for another octave. Attention to spurious structural resonances is important. A general overview of developing the device with attention to its design, high-power application, and problem areas will be presented. [Work supported by ONR.]
There are no rules? Perceptual challenges posed by large-scale, three-dimensional surround-sound systems
Authors: Field Ambrose
Published: February 2014

With the widespread adoption of multichannel audio gaining pace, sound designers have recognized that surround-sound systems are not simply another effects process that can be applied retroactively to musical material. This discovery has generated complex questions, e.g., where to place instruments, sounds, or dialog in a three-dimensional mix? Rather than attempting to prescribe ways in which composers can physically spatialize their material, this work proposes that by understanding the need to spatialize sound, informed methods of three-dimensional projection can be generated. Ways in which sound designers can conceive their material for surround-sound directly from the outset are examined, as is the premise that there is a need to recognize that each sound within a mix will have its own pre-existing spatial context. The relationship between the initial context in which a recording was made, and how that sound is finally spatialized plays a significant part in how ‘‘believable’’ a soundfield is. This different approach to surround mixing is detailed, demonstrating that the traditional practice of sound placement according to what a sound is can be detrimental to establishing convincing and functional surround soundfields. Finally, practical examples are given, relating to and integrating Dolby 5.1 and Ambisonics diffusion techniques.
I-INCE Technical Initiative ♯4: Noise and reverberation control for schoolrooms
Authors: Lubman David , Sutherland Louis C.
Published: February 2014

The International-INCE General Assembly approved Technical Initiative ♯4 in December 1999. The initiative creates an internationally coordinated program intended to assist participating nations with engineering issues associated with achieving satisfactory acoustics in learning spaces. Representatives of various acoustical societies were appointed to a Technical Study Group, convened by Zerhan Karabiber, professor of architecture at Yildiz University in Turkey. The initiative was well received and the group has representatives from 17 acoustical societies in 15 nations. The group is directed to submit its draft report for review by the I-INCE General Assembly by August of 2002. The report is expected to provide practical guidance to school planners, designers, code officials, and policy makers. The group met at the Inter-Noise 2000 in Nice, France. It will meet again at Inter-Noise 2001 at The Hague. An assignment made to all representatives is to assess the state of classroom acoustics and related activities in their own countries. This presentation briefly highlights energetic US activities. These include development of a draft ANSI Standard for classroom acoustics, and development of educational materials (led by the Acoustical Society of America), activities and support by other professional, acoustical, hearing, and governmental organizations, and critizen activism.
A comparison of auditory suppression in older and younger normal-hearing adults
Authors: Gehr Sara Elizabeth , Sommers Mitchell
Published: February 2014

The present study was designed to assess the effect of age, independent of hearing loss, on auditory suppression. Two-tone suppression in a forward masking paradigm was measured for normal-hearing older (65–75 years old) and normal-hearing younger (19–24 years old) adults. Thresholds for detecting a 2000 Hz sinusoid were measured in conditions where the forward masker either contained one (nonsuppressive) or two (suppressive) tones. Young adults showed reduced thresholds in the suppressive, compared with the nonsuppressive condition. In contrast, thresholds in the suppressive and nonsuppressive conditions did not differ for older adults. This lack of a difference between the suppressive and nonsuppressive conditions for the older adults indicates that they have reduced suppression compared with young adults. Implications for the mechanisms mediating auditory suppression are discussed. [Work supported by American Psychological Association.]
Detection of gaps marked by frequency-asymmetric tonal complexes
Authors: Grose John H. , Hall Joseph W. , Buss Emily
Published: February 2014

When the frequency content of two acoustic markers bounding a temporal gap is asymmetric across the gap, then sensitivity to the gap depends on the order in which the markers are presented [Formby et al., J. Acoust. Soc. Am. 104, 984–998 (1998)]. Specifically, when one marker consists of a single tone while the other marker consists of that same tone plus a second synchronous tone, then performance is better when the leading marker is the two-tone complex. Analogous results have been found for cochlear implant listeners when the number of electrode channels marking the gap is asymmetric across the gap [van Wieringen and Wouters, J. Acoust. Soc. Am. 106, 1925–1939 (1999)]. The present study extended this basic finding to conditions where the synchronous second tone within the two-tone marker was presented either diotically, or to the ear contralateral to that receiving the remaining tone (and the single-tone marker). Temporal asynchronies were also introduced into the two-tone marker in an effort to weaken the perceptual fusion of the tone pair. Results from six normal-hearing listeners indicated that the basic order effect was present for the monaural, diotic and dichotic conditions. [Supported by NIH NIDCD R01-DC01507.]
Modulation masking produced by masker modulation tone complexes
Authors: Verhey Jesko L. , Ewert Stephan , Dau Torsten
Published: February 2014

Thresholds were measured for detecting a sinusoidal amplitude modulation in the presence of a masker-modulation tone complex. Both modulations were applied to the same sinusoidal carrier. Two different masker modulations were used: (i) a pair of components beating at the signal-modulation frequency and (ii) a three-tone complex producing a sinusoidal amplitude modulation in the modulation domain whereby the frequency of the slow amplitude variation was equal to the signal-modulation frequency. Masked thresholds were measured as function of the phase of the signal modulation relative to the slow amplitude variation in the masker modulation. In all conditions, thresholds were lower for an in-phase signal modulation compared to an antiphase condition. The maximum threshold difference was 15 dB. The results are in contrast to recent data [B. C. J. Moore et al., J. Acoust. Soc. Am. 106, 908–918 (1999)], where the lowest thresholds were obtained for the antiphase condition. Our data are in line with the idea that a nonlinearity prior to the modulation filterbank extracts the slow variation of the masker modulator. The data could be fitted well by assuming a combination of a peripheral (power-law) compression and a threshold. Peripheral compression alone did not account for the data.
Asymmetry of masking in the envelope-frequency domain
Authors: Ewert Stephan , Dau Torsten , Verhey Jesko L. , Kollmeier Birger
Published: February 2014

Masked modulation thresholds can be influenced by the detection of amplitude fluctuations of the envelope (referred to as the venelope in the following) which arise from either beating between the masker modulation and the probe modulation, or from the intrinsic envelope fluctuations of a narrowband-noise modulator itself. It was tested to see to what extent the detection of venelope fluctuations is involved in corresponding tone-in-noise, noise-in-tone, and tone-in-tone modulation masking conditions. Modulation frequencies in the range from 20–100 Hz, applied to a 2.8-kHz sinusoidal carrier, were used. Thresholds in the noise-in-tone condition are always lower than those in the tone-in-noise condition, comparable with the asymmetry of the masking effect in the audio-frequency domain. In general, it was observed that (1) subjects use venelope fluctuations as a detection cue, and that (2) venelope fluctuations interfere with an additionally applied amplitude modulation when both fall into the same frequency range. To interpret the empirical findings, a general model structure for the processing of envelope and venelope fluctuations is proposed. Similarities between the auditory system’s coding strategies for audio frequencies/envelope fluctuations and envelope frequencies/venelope fluctuations are discussed.
Phase effects in masking in normal-hearing and hearing-impaired listeners
Authors: Dau Torsten , Oxenham Andrew J.
Published: February 2014

Changes in the phase relationships between components in a harmonic tone complex masker can lead to large changes in masked threshold for long-duration sinusoids in normal-hearing listeners. The effect is reduced or absent in hearing-impaired listeners. This reduction could be due to a loss of peripheral compression, a change in the auditory filters’ phase response, or both. Signal thresholds were measured as a function of masker phase curvature, signal frequency, and masker fundamental frequency (F0). In contrast to previous studies, more than just two phase relationships were considered, allowing us to compare the overall phase response of impaired and normal ears. Peripheral compression was estimated in a separate experiment using a notched-noise masking technique. If changes in filter phase response can account for the differences between normal-hearing and hearing-impaired listeners, then certain phase relationships should produce large threshold differences even in hearing-impaired listeners. If peripheral compression is important, threshold differences in hearing-impaired listeners should emerge at very low F0s, due to the predicted interaction between peripheral compression and temporal processing at higher stages. Preliminary results suggest that the difference between normal-hearing and hearing-impaired listeners can be explained primarily in terms of peripheral compression. [Work supported by DFG and NIDCD.]
Informational masking as a function of masker set size
Authors: Richards Virginia M. , Tang Zhongzhou
Published: February 2014

Thresholds for the detection of a 1000-Hz tone added to informational maskers were measured using six-tone maskers. A large number of different maskers were generated by randomly choosing the frequencies of the six tones from a (log) uniform distribution ranging from 100 to 6000 Hz, exempting the 160-Hz frequency range surrounding the 1000-Hz signal. These maskers were then assigned to different masker sets, with the number of maskers in any one set being 3, 6, 12, or 24. Thresholds were measured separately for the different masker sets. Unlike the method used by Wright and Saberi [J. Acoust. Soc. Am. 105, 1765–1775 (1999)], on each interval the masker was drawn with replacement. For small set sizes, the trials could be segregated into those in which the maskers were different across intervals and those in which the maskers were the same across intervals. The resulting thresholds did not depend on the masker composition in the two intervals. As the set size increases, the observers ability to remember/identify the maskers is diminished but the average thresholds are not obviously altered by changes in set size beyond 3. [Work supported by NIH.]
Using reproducible noise to illuminate the nature of informational masking
Authors: Gilkey Robert H. , Mason Christine , Kidd Gerald
Published: February 2014

Informational masking has been distinguished from energetic masking in that it seems to depend less on the specific characteristics of the stimulus presented on a particular trial (e.g., energy in the critical band) and more on the variability in the ensemble of stimuli presented across trials. We employ techniques that have been used in reproducible noise masking experiments [D. M. Green, Psychol. Rev. 71 (1964)] to examine the degree to which subjects responses in informational masking tasks are driven by the characteristics of the individual maskers. A single-interval task was used to collect hit and false–alarm rates to individual maskers under multiple-burst-same (MBS) and multiple-burst-different (MBD) conditions [G. Kidd et al., J. Acoust. Soc. Am. 95 (1994)]. During each block the 25 MBS or 25 MBD reproducible maskers were presented in random order across trials. Both hit and false–alarm rates showed significant dependence on the masker waveform under both MBS and MBD conditions (p<0.001). Preliminary modeling efforts suggest that the subjects responses are at least weakly related to the energy near the signal frequency in the individual masker-alone and masker-plus-signal waveforms. [Work supported by NIH and OBR.]
Increasing informational masking by contralateral stimulation
Authors: Kidd Gerald , Mason Christine R. , Arbogast Tanya L. , Brungart Douglas S. , Simpson Brian D.
Published: February 2014

Although informational masking is thought to reflect central mechanisms, substantial reductions in informational masking generally occur when the target and masker are presented to different ears. Recently, Brungart and Simpson [J. Acoust. Soc. Am.] found that the intelligibility of a target phrase in a monaural two-talker stimulus was severely degraded by the addition of an unrelated speech signal to the contralateral ear. Their results suggest that the presence of an informational masker in the unattended ear can increase informational masking in the target ear. In this study parallel experiments using nonspeech informational maskers determined whether similar results are obtained in nonspeech detection tasks. The stimuli were sequences of multitone bursts arranged in spectrotemporal patterns that produce very large or very small amounts of informational masking. The signal was a sequence of 1000-Hz tone bursts played synchronously with the maskers. Combinations of effective and ineffective informational maskers were presented in the ear ipsilateral to and contralateral to the signal. Control conditions (masker ipsilateral/contralateral only) established baseline performance. The results supported the earlier findings for multiple-talker conditions. This suggests that the phenomenon is not restricted to speech and may reflect more general perceptual processes accessible through contralateral stimulation. [Supported by NIDCD and AFOSR.]
Consonant recognition in noise with temporal cues. III. Effects of temporal envelope enhancement on identification thresholds
Authors: Apoux Frederic , Garnier Stephane , Lorenzi Christian
Published: February 2014

In order to test the effect of temporal envelope enhancement on speech perception, masked identification thresholds of aCa stimuli (C=p,t,k,b,d,g,f,s,ch,v,z,j) were measured in a two-interval, four-alternative forced choice procedure, using two randomly interleaved two-down/one-up, adaptive staircases. aCa stimuli were either temporally expanded or left intact. The expanded stimuli were obtained by multiplying the original signal by the original envelope at each corresponding point in time. The masker was a gated, steady speech-shaped noise. Temporal expansion was not applied to noise. Thirty normal-hearing listeners (19–28 years) and 42 hearing-impaired listeners (48–79 years) participated in this experiment. Overall, the results showed that thresholds were slightly lower when the envelope was expanded rather than left intact. Moreover, a detailed analysis of the data revealed that only one consonant was adversely affected by envelope expansion (+2 and +3 dB) in both groups. In normal-hearing listeners, a 2-, 4-, and 5-dB improvement was found for consonants f, k, and j, respectively. In hearing-impaired listeners, the results showed that identification thresholds were improved by 3.5 dB for voiced consonants. In this group, the identification thresholds of five consonants (t,b,d,g,z) were substantially lowered by expansion by 2 to 9 dB.
The application of complex layer analysis to the vibrating fluid-loaded elastic plate
Authors: Feit David , DiPerna Daniel T.
Published: February 2014

Structural acoustics’ canonical problem—the locally driven fluid-loaded elastic plate attracted David Crighton’s attention over much of his career, and was the subject of his 1998 Rayleigh Medal Lecture to the British Institute of Acoustics. During this lecture he showed it ‘‘to contain a great richness of effects.’’ This presentation further elucidates the problem using an approach we refer to as complex layer analysis (CLA). CLA replaces the fluid half-space into which the plate radiates by a layer of acoustic fluid of finite thickness H=H0(1+iη) that is a complex number. By formulating the fluid-structure interaction problem in this manner the Fourier transformed surface pressure-velocity relationship which usually contains branch point singularities is approximated as a rational function of the transform variable. With the branch cut singularity removed, the resulting inverse Fourier transform is easily evaluated analytically, using contour integration, as a sum over a small number of poles. Each pole corresponds to a wave propagating in the fluid/structure system. The location of these poles is found analytically using a perturbation technique. Results for the radiation from a line-driven plate show excellent agreement with published results. This approach permits explicit evaluation and differentiation between the surface waves, i.e., the fluid-loaded structural waves and those associated with the acoustic field as affected by the plate’s structural parameters. [Work supported by CDNSWC ILIR Program.]
Approximation of plate edge diffraction
Authors: Norris Andrew
Published: February 2014

Edge diffraction from thin plates and structural elements remains an area closely connected with the name of David Crighton. He developed the tools for solving the Wiener–Hopf problems that were inevitably obtained, and derived useful asymptotic approximations under light and heavy fluid loading. His approach and his philosophy of obtaining physical insight are applied in this lecture to the fundamental configuration of a semi-infinite thin plate in a fluid. The acoustic diffraction coefficient is strongly dependent upon frequency, unlike the analogous coefficients from hard or soft screens. At low frequencies the diffraction is like that from a soft or pressure release screen, while at high frequencies the hard screen approximation is more appropriate. An approximate but simple diffraction coefficient is proposed which has the correct limiting behavior at low and high frequencies. The transition from the low to high frequency response occurs when the acoustic wavelength matches the ratio of the areal to volumetric densities of the plate and fluid. The approximate formula is compared with the exact diffraction coefficient, showing good agreement for all frequencies.
Long and finite time approximations of high modal density systems
Authors: Barbone Paul E.
Published: February 2014

Our recent results concerning modeling of undamped structures with high modal density show that such structures can be replaced by very simple structures with damping. In the extreme case, a structure with infinitely many degrees of freedom can be replaced by a single mass-dashpot-spring system. When applied to a particular structure, however, such a model has a finite time of validity, predicted to be T=O(Δω)−1. Here, Δω represents the spacing of natural frequencies in the original structure. In this contribution, we present models valid for simulation times T≫(Δω)−1. The new models are based on long time rather than high modal density approximations. We show how the two models can be combined to form a single model which gives accurate results for all times.
With a pinch of dissipation all operators can be inverted
Authors: McCoy John J.
Published: February 2014

With domination of computation over analysis, issues of convergence and uniqueness have largely given way in the engineering/physics literature to issues of numerical stability. A common cause is sometimes the genesis of a lack of convergence or of uniqueness when seeking an analytical prediction, and of a numerical instability when seeking a numerical prediction. If the underlying cause is the same, the actions prompted are sometimes quite different. The introduction of dissipation is widely accepted as a ‘‘tool’’ for ‘‘regularizing’’ numerical codes, by virtue of incorporating a truer physics into the model. Three experiment scenarios are described for which the introduction of dissipation also serves to ‘‘mask’’ errors in the development behind the code, thereby precluding the prediction of significant physical effects. Two of the scenarios are drawn from the published literature—the errors in modeling arise in including finite frequency effects in the scattering by a rough surface, and in including inclusion/inclusion interaction in estimates of the settling rate for nondilute fluid suspensions. The third scenario has not been discussed in the published literature—the modeling error applies to the generalization of a nonreflecting boundary condition at an interior plane of an unbounded range-independent full space, to now model the reflection that obtains at a plane interface connecting two, dissimilar range-independent half-spaces.
Insuring causality of frequency-response functions with hysteretic damping
Authors: Strasberg M.
Published: February 2014

When calculating the temporal response h(t) of a system responding linearly to an external impulsive force applied at t=0, the availability of personal computers that calculate Fourier transforms may make it convenient to first calculate the frequency-response function H(ω) of the system and then obtain h(t) as the inverse Fourier transform of H(ω). Dissipation can be accounted for by multiplying the stiffness and elastic quantities in H by the complex factor (1+iη), assuming ‘‘hysteretic’’ damping with loss factor η. However, this makes H a complex function of frequency whose inverse transform may be neither real nor causal. As is well known, the inverse transform can be made real by setting H(−ω)=H*(+ω), where * indicates complex congugate, or replacing η with ηsgn(ω), where sgn(±ω)=±1. But this may not lead to causality. It is suggested that causality be insured by expressing the temporal function simply as h(t)=[1+sgn(t)]ĥ(t), where ĥ(t) is the inverse Fourier transform of either the real or the imaginary part of H(ω), not both. It will be shown that this is just what the Kramers−Kronig causality relations require.
On the spatial coupling between deterministic and fuzzy subsystems in the hybrid approach to the midfrequency problem
Authors: Shorter Philip J. , Gardner Bryce K.
Published: February 2014

The analysis of the dynamic behavior of a structural–acoustic system across a broad frequency range presents a number of challenges to an analyst. For a typical structural–acoustic system it is quite common to find that the modal density varies significantly between the various subsystems, across the frequency range of interest. The vast number of modes in the system as a whole can render a detailed deterministic analysis impractical, while the low modal density of certain subsystems is problematic for statistical energy analysis. One approach to the problem is to construct a hybrid model that combines deterministic and statistical descriptions of the system dynamics. One of the key requirements of the hybrid approach is an accurate estimate of the spatial coupling that occurs between the deterministic and statistical (or fuzzy) parts of the model. This paper discusses recent work which has investigated both a spatial correlation approach to calculating this coupling and also an asymptotic modal approach. The relative merits of the different approaches are discussed and a number of numerical examples are presented.
The effect of a non-native accent in Dutch on speech intelligibility
Authors: van Wijngaarden Sander J. , Steeneken Herman J. M. , Houtgast Tammo
Published: February 2014

It is well known that second-language talkers are usually less intelligible than native talkers, especially under adverse listening conditions. Background noise tends to influence the intelligibility of foreign accented speech more profoundly than unaccented speech. In order to quantify this effect, speech reception threshold (SRT) experiments were carried out using Dutch speech by American, German, Polish, Chinese and (native) Dutch talkers (15 speakers, 3 talkers per language background). The experience with the Dutch language varied between talkers from 3 months to 28 years. Ten Dutch university students participated as listeners. In order to obtain 50% sentence intelligibility, non-native talkers were found to require a 0–3-dB better speech-to-noise ratio than native talkers do. A significant correlation between self-reported proficiency and SRT-score was observed (R=0.78). Also, an objective estimate of the degree of foreign accent of the individual speakers was obtained by means of a pairwise comparison experiment, in which 19 native Dutch listeners participated. The accent ratings which were obtained (after Thurstone normalization) were also significantly correlated with the SRT-scores (R=0.85). The conclusion may be drawn that the effect of noise on the intelligibility of foreign accented speech can be predicted quantitatively from easily obtained measures of perceived foreign accent.
Effects of noise and proficiency level on intelligibility of Chinese-accented English
Authors: Rogers Catherine L. , Dalby Jonathan M. , Nishi Kanae
Published: February 2014

It is known that native speech intelligibility is degraded in background noise. This study compares the effect of noise on the intelligibility of English sentences produced by native English speakers and two groups of native Mandarin speakers with different English proficiency levels. High-proficiency Mandarin speakers spoke with detectible accents, but their speech was transcribed at about 95% of words correct in a previous study, in which no noise was added [C. Rogers and J. Dalby, J. Acoust. Soc. Am. 100, 2725 (1996)]. Low-proficiency Mandarin speakers were transcribed at about 80% correct in the same study. Forty-eight sentences spoken by six speakers (two native, two high proficiency, and two low proficiency) were transcribed by listeners under four conditions: with no added noise and mixed with multi-talker babble at three signal-to-noise ratios (+10, 0, and −5 dB). Transcription accuracy was poor for all speakers in the noisiest condition, although substantially greater for native than for Mandarin speakers. For the other three conditions, the rate of degradation of intelligibility with increasing noise was much greater for accented than for native speech. These results confirm and extend those reported in Munro [Stud. Sec. Lang. Acq., 139–153 (1988)]. [Work supported by University of South Florida.]
Cross-language perception of rate induced resyllabification
Authors: Nagao Kyoko , Lim Byung-jin , de Jong Kenneth
Published: February 2014

This paper investigates the degree to which speakers of languages with different syllabic inventories are similar in their perceptions of syllabic affiliation. Stetson (1951) noted that repeated coda (VC) structures become perceived as onset (CV) structures as repetition rates increase. Stimuli were extracted from a repetitive production experiment in which English talkers produced voiced and voiceless labial stop onsets and codas at tempi controlled by a rate varying metronome. Native English, Japanese, and Korean listeners were asked to label the repeated syllable with one of four choices: ‘‘bee,’’ ‘‘pea,’’ ‘‘eeb,’’ ‘‘eep.’’ All three language groups showed perceptual shifts from VC to CV as the speech rate increased. However, Japanese listeners are biased toward identifying VC productions as CVs, and very rarely identified CV productions as VCs. These results indicate a very consistent cross-language perception of syllabic affiliation, regardless of a language’s syllabic inventory, although the language’s inventory does have a small effect on such perceptions. These results differ from those for the voicing contrast. Voicing contrasts in coda position which are non-native for Koreans were more poorly categorized by the Korean listeners. [Work supported by NIDCD and NSF.]
A cross-linguistic study on discourse and syntactic boundary cues in speech
Authors: Fon Janice , Johnson Keith
Published: February 2014

Online segmentation is a formidable task for any speech parser. Yet, human beings seem to handle this task with ease. This study focuses on the relationship between discourse/syntactic boundaries and prosodic cues in divergent languages—English, Japanese, and two varieties of Mandarin (Guoyu and Putonghua). Speech was elicited by having talkers describe the events in a film [W. L. Chafe (unpublished)]. Recorded data were transcribed, digitized, and will be segmented into discourse and syntactic units while measurements of F0, syllable duration, and rms amplitude will be taken on the digitized data. Prosody will be partially labeled following ToBI (Tones and Break Indices) conventions of each language. A comparison of different dimensions of data-discourse/syntax, acoustics, and intonation, will be made in order to examine boundary cues in speech. Our previous work using a smaller set of Mandarin (Guoyu) data has shown that syllable onset interval isochrony is generally preserved until the pre-boundary syllable. Pre-boundary syllables are characterized by a significant lengthening effect, which differs by boundary types. Lengthening before discourse units is longer than that before syntactic units such as clauses or phrases. [Work supported by NIDCD.]
High-speed acoustic communication in shallow water using multiple coherent path beamformer technique
Authors: Beaujean Pierre-Philippe J. , LeBlanc Lester R.
Published: February 2014

A multiple coherent space-time processing method is used for acoustic communication at high data rate in very shallow water, between 16 and 32 kHz. The multiple coherent path beamformer (MCPB) method for processing the signals uses an adaptive processor that forms beams in the direction of a collection of coherent signals representing the strongest path. The source is the FAU Utility Acoustic Modem used for acoustic networking during AUV operations. The system encodes data using coherent modulation schemes with coded rates varying between 4000 and 48000 bps. The receiver system is composed of a 64-channel Mills–Cross array attached to an FAU embedded 64-channel acquisition system. Results already obtained show that the MCPB can decode data reliably at 3200 m for rates up to 32000 bps, with a platform speed of 2–3 knots and a sea-state of 1–2. For a source level of 186 dB, BPSK encoding and 62.5&♯61549;s symbols (16000 bps), the MCPB achieves a bit error rate of 0.2% without any Forward Error Coding. These results demonstrate the long-range and high-data rate transmission ability of the system, and make possible real-time transmission of side-scan data and other low-resolution video images.
A channel subspace filtering approach to adaptive equalization of realistic acoustic channels
Authors: Nadakuditi Raj R. , Preisig James C.
Published: February 2014

One of the major problems in underwater acoustic communications is compensating for the large amount of time varying intersymbol interference (ISI) due to multipath. Associated with each of the deterministic propagation paths are macro-multipath fluctuations which depend on large scale environmental features and geometry and micro-multipath fluctuations which are dependent on small scale environmental inhomogeneities. For arrivals which are unsaturated or partially saturated, the fluctuations in the ISI are dominated by the macro-multipath fluctuations resulting in correlated fluctuations between different taps of the sampled channel impulse response. Traditional recursive least squares (RLS) algorithms used for adapting channel equalizers do not exploit this structure. A post-filtering algorithm is presented to exploit this channel correlation structure in least squares based channel estimators and equalizers. The improvement in the performance of the algorithm with respect to the traditional least squares algorithm is predicted theoretically and demonstrated using both simulation and experimental data.
Quantitative bit error analysis of time-reversal communication sequences
Authors: Edelmann G. F. , Akal T. , Hodgkiss W. S. , Kim S. , Kuperman W. A. , Song H. C.
Published: February 2014

Underwater acoustic communications must mitigate the intersymbol interference caused by the time-varying multipath dispersion. An experiment was conducted in June 2000 demonstrating that the time-reversal process recombined the temporal multipath resulting in reduced bit errors for communication. Quantitative bit error results will be shown for BPSK (binary phase shift keying) and QPSK (quadrature phase shift keying). Communication sequences were transmitted over a distance of 10 km both in range-independent and range-dependent environments north of Elba Island, Italy. The range-independent transmissions were made in 100-m-deep water and the range-dependent transmissions were made upslope from 100-m-deep water into 40-deep-water. [Work supported by ONR.]
Passive phase-conjugate signaling using pulse-position modulation
Authors: Hursky Paul , Porter Michael B. , McDonald Vincent K. , Rice Joseph A.
Published: February 2014

Acoustic communications is an attractive option for networking distributed assets, such as UUVs, autonomous sensors, and other systems that must talk to one another in the ocean. Although the ocean is often a complex multipath channel, impressive progress has been made in developing equalization algorithms to overcome this. Unfortunately, many of these algorithms are computationally demanding and not as power efficient as we would like, operating at the bottom of the ocean. At the same time, the networking applications being envisioned often also require low rate, but highly reliable signaling, for purposes such as wakeup. The passive phase-conjugate concept [J. Acoust. Soc. Am. 95, 1450–1458 (1994)] is a very simple demodulation technique which nevertheless is coherent and can overcome signal distortion due to multipath. To explore its use in low power, lightweight applications, we have extended this approach to use pulse-position modulation (PPM) and have tested it during several SignalEx experiments using an 8–16 kHz band. We present results of these tests, discuss synchronization and Doppler compensation, and compare the PPM signaling scheme to frequency-shift keying, which is often also considered for low power, lightweight applications.
Using continuous additive training sequences for high rate, Doppler tolerant communications
Authors: Collins Tim , Atkins Philip R. , Bongiovanni Claire , Davies Jon J. , Dunn Shaun M. , Pointer Steve A.
Published: February 2014

An underwater acoustic communications system designed to transmit 20 kbit/s over ranges from 100 m up to 5 km between a semi-autonomous underwater vehicle and a surface vessel moving with up to 20 knots relative velocity is presented. Under these conditions, attention must be given not only to the steady-state equalization capability of the receiver, but also to its ability to respond to sudden changes in channel profile due to sudden movements of the remote vehicle. In addition to conventional packet-based transmissions, a novel continuous transmission system was also implemented during the experimental stages. Instead of using distinct channel probe, training and data blocks, a continuous training sequence was added on top of a continuous data transmission. Advantages of continuous additive training sequences (CATS) such as an improved tolerance to burst errors, greater data throughput and flexible re-synchronization ability will be highlighted. These are balanced against the disadvantages of increased receiver complexity and compromised ambient noise performance. Results of several sea-trials will be presented to verify the performance of the system at short and long ranges using both static and dynamic platforms. [Work sponsored by DERA Winfrith, UK.]
Sea trial results of a robust and spectral-efficient OFDM underwater communication system
Authors: Kim Byung-Chul , Lu I.-Tai
Published: February 2014

In single-carrier, high data-rate systems symbol durations are much smaller than channel delay spreads. Reliable equalization in such systems is extremely difficult to attain because the channel is time varying and highly frequency selective. One way to circumvent the need of using costly equalization schemes, while maintaining high data rates, is to use multicarrier modulation in which broadband data is transmitted in parallel on multiple narrowband subcarriers. Symbol duration T in such systems is usually larger than delay spreads such that each narrowband subcarrier experiences only nonfrequency-selective flat fading. To improve spectral efficiency and eliminate the use of guard bands between subcarriers, each subcarrier can be chosen to be orthogonal to the others. Such a multicarrier system is referred to as orthogonal frequency division multiplexing (OFDM). Unfortunately, the orthogonality is destroyed in typical underwater channels due to large Doppler shifts and spreads (compared to the inverse of symbol durations). Therefore, previous work in UWA required the spacing of adjacent subcarriers to be 2/T, which is twice the minimum spacing 1/T. In this paper, time-rescaling and pilot-symbol aided channel estimation techniques are employed to combat Doppler shift and spreads. Reliable results are obtained with 1/T subcarrier spacing in sea trials.
Listening and learning in classroom acoustical design
Authors: Petry Elizabeth , McClellan James , Myler Patricia
Published: February 2014

Listening and learning are proven ingredients to the successful education of our nation’s children. Research studies confirm that the acoustical environment in a classroom is an important variable in the academic achievement of children. For effective communication in a classroom, unoccupied ambient noise levels should not exceed 30 to 35 dBA, while reverberation times (RT) should not surpass 0.4 s. Unfortunately, these acoustic conditions are seldom found. Even children with ‘‘normal’’ hearing sensitivity often encounter significant difficulty understanding noisy or reverberated speech. Excessive classroom reverberation and/or noise can compromise speech perception, but also reading/spelling ability, behavior, attention, concentration, and academic achievement in children with normal hearing and in children with hearing loss. The concept of an ideal acoustical classroom environment provides design, engineering, and budgetary challenges for architects, engineers, school administrators, and community leaders. To address these somewhat conflicting challenges, a team of architects and engineers has collaborated to develop successful auditory and architectural solutions. These real life solutions in Connecticut schools, John Trumball Primary School, Watertown; Rochambeau Middle School, Middlebury; and East Lyme High School, East Lyme will serve as models to other communities, educators, planners, and architects as we enter the new millennium.
Subjective evaluation of speech transmission quality in rooms with sentence materials
Authors: Sato Hiroshi , Kanda Jun , Nishitani Shuichi , Yoshino Hiroshi , Morimoto Masayuki
Published: February 2014

The situation is often encountered that the score of syllable, word or sentence intelligibility test or measured indexes of speech intelligibility (i.e., STI, RASTI) is different from the listeners impression. This is caused by the difference between subjective impression and speech information recognition. Four kinds of listening tests were performed to obtain a subjective evaluation for speech transmission in auditoria; (a) easiness of speech perception by paired comparison method, (b) easiness of speech perception by rating scale method, (c) acceptability of speech perception by yes–no-form method, (d) difficulty of sentence listening. The results from method (a) treated as a standard data because of its accuracy. The results demonstrate that (1) easiness of speech perception presented only relative value, (2) acceptability is not suitable for rating the speech transmission quality of sound fields because of the difficulty of judgment, (3) difficulty is easy to understand from its meanings and gives absolute evaluation.
Pretreatment with low-energy (12 kV) shockwave lithotripsy (SWL) protects kidney from subsequent high-energy application
Authors: Evan Andrew , Willis Lynn , Connors Bret , Blomgren Philip , Shao Youzhi , Lingeman James
Published: February 2014

A clinical dose of 2000 shockwaves applied at 12 kV induces renal vasoconstriction but causes no hemorrhagic lesion. Two thousand shockwaves applied at 24 kV causes the same vasoconstriction as 12 kV but lesion size is increased. These findings led us to ask whether lesion size would be smaller after 2000 shockwaves at 24 kV to one pole if a vasoconstrictive state was induced in that kidney by first applying 2000 shockwaves at 12 kV to the lower pole of that kidney. Anesthetized pigs received 2000 shockwaves to the lower pole followed by 2000 shockwaves to the upper pole of the same kidney. Structural and functional analyses were performed 4 hours post-SWL. Results from these experiments show renal vasoconstriction induced from the first application of SWL at 12 kV to one pole appears to limit bleeding/hemorrhage caused by 24 kV to the other pole.
Generation of very high-pressure pulse using time reversal in a solid waveguide: Application to lithotripsy
Authors: Montaldo Gabriel , Roux Philippe , Derode Arnaud , Fink Mathias , Neigreira Carlos
Published: February 2014

The use of a piezoelectric transducers array has opened the possibility of electronic steering and focusing the beam to track the stone. However, due to the limited pressure delivered by each transducer (typically 10 bars), the number of transducers needed to reach the focus an amplitude of the order of 1000 bars is typically of some hundred of elements. Here, we present a new solution that combines the use of the time reversal method with a small number of transducers that generate low-amplitude waveforms in a solid waveguide to obtain the shock wave of very high amplitude in tissues located at the front of the waveguide. We use the fact that, due to time reversal invariance, for every burst of ultrasound diverging from a source and reflected by the boundaries of the waveguide, there exists in theory a set of waves that retraces all of these complex paths and converges in synchrony, at the original source. As the temporal dispersion of the waveguide increases, the time reversed wave is temporally recompressed with a stronger amplitude amplification. Such an effect allows a very high spatio-temporal recompression to be reached and to obtain a small number of transducers the amplitude needed to break stones.