bluuebunny/crossref_metadata_2025 huggingface dataset:
Event synchronous sinusoidal model based on frequency-to-instantaneous frequency mapping
Authors: Zolfaghari Parham , Banno Hideki , Itakura Fumitada , Kawahara Hideki
Published: October 2013

We describe a glottal event synchronous sinusoidal model for speech analysis and synthesis. The sinusoidal components are event synchronously estimated using a mapping from linearly spaced filter center frequencies to the instantaneous frequencies of the filter outputs. Frequency domain fixed points of this mapping correspond to the constituent sinusoidal components of the input signal. A robust technique based on a wavelet representation of this fixed points model is used for fundamental frequency extraction as used in STRAIGHT [Kawahara et al., IEICE (1999)]. The method for event detection and characterization is based on group delay and similar fixed point analysis. This method enables the detection of precise timing and spread of speech events such as vocal fold closure. A trajectory continuation scheme is also applied to the extracted sinusoidal components. The proposed model is capable of high-quality speech synthesis using the overlap–add synthesis method and is also applicable to other sound sources. System evaluation results using spectral distortion measures and mean opinion scores will be reported. A comparison with the fixed frame-rate sinusoidal models will be given.
Spectral variability of /s/ in sV and sCV sequences produced by adults and children
Authors: Munson Benjamin
Published: October 2013

Previous research has demonstrated that both children and adults produce /s/ with greater spectral variability in /sp/ sequences than /st/ sequences, when these sequences are embedded in the medial position of CVCCVC nonwords [B. Munson, J. Acoust. Soc. Am. 110, 1203–1206 (2001)]. The current study examined whether this result could be replicated when /s/ is embedded in syllable-onset clusters, with a variety of following consonants and vowels. Adults and children aged 3–7 were recorded producing multiple tokens of sV and sCV nonwords, where the vowel was either /i/, /ɑ/, or /u/, and the consonant was either /p/, /t/, /w/, or /l/. For each token, the spectral mean of non-overlapping 10-ms windows of frication noise was calculated. Nonlinear regressions of the form y=aebx were used to predict the spectral mean of each portion of frication noise from its position in the fricative. The resulting measure of model fit, R2, was used as an index of within-speaker variability. For each participant, separate R2 values were calculated for /s/ in each of the 15 phonetic contexts. Analyses will address the influence of age, consonant context, and vowel context on spectral variability.
Characteristics of diadochokinesis in Parkinson’s Disease and Multiple Sclerosis
Authors: Tjaden Kris , Watling Elizabeth
Published: October 2013

The current study applies a quantitative, acoustic analysis procedure for the study of rapid syllable productions outlined by Kent and colleagues [R. D. Kent et al., J. Med. Sp. Lang. Path. 7, 83–90 (1999)] to syllables produced by speakers with Parkinson’s Disease and Multiple Sclerosis. Neurologically healthy talkers will be studied for comparison purposes. Acoustic measures will be reported for syllable repetitions of /pə/, /tə/, and /kə/. Temporal measures will include syllable duration, syllable rate, and stop gap duration. The energy envelope of syllable repetitions will be quantified using measures of rms amplitude minima and maxima. Acoustic measures will be contrasted to determine the extent to which acoustic profiles of diadochokinesis distinguish hypokinetic dysarthria associated with Parkinson’s Disease, ataxic dysarthria secondary to Multiple Sclerosis, and spastic dysarthria secondary to Multiple Sclerosis. It also is of interest to determine whether speakers with Parkinson’s Disease and Multiple Sclerosis judged to be nondysarthric via perceptual analyses also demonstrate objective, acoustic profiles of diadochokinesis that are within normal limits. [Work supported by NIH.]
The acoustic features of human laughter
Authors: Bachorowski Jo-Anne , Owren Michael J.
Published: October 2013

Remarkably little is known about the acoustic features of laughter, despite laughter’s ubiquitous role in human vocal communication. Outcomes are described for 1024 naturally produced laugh bouts recorded from 97 young adults. Acoustic analysis focused on temporal characteristics, production modes, source- and filter-related effects, and indexical cues to laugher sex and individual identity. The results indicate that laughter is a remarkably complex vocal signal, with evident diversity in both production modes and fundamental frequency characteristics. Also of interest was finding a consistent lack of articulation effects in supralaryngeal filtering. Outcomes are compared to previously advanced hypotheses and conjectures about this species-typical vocal signal.
The distribution of phonation type index k
Authors: Park Hansang
Published: October 2013

A phonation type index k was proposed to account for variation in the phonation type. (Park, 2001) In this study we investigated the distribution of the phonation type index k to see a mode of the phonation type. The distribution of the phonation type index k is expected to be multimodal if a phonation type is sustained through the entire vowel. However, it is expected to be unimodal if the phonation type difference is not so significant or if distinct phonation types are not maintained through the entire vowel but occur only at earlier part of the vowel. An experiment was conducted with Standard Korean data that have three linguistically distinct phonation types: aspirated, lenis, and fortis. The results showed that the distribution of the phonation type index k was unique to each speaker. The distribution of the phonation type index k was close to bimodal for one speaker while unimodal for the other two speakers. The distribution of the phonation type index k also showed differences in mean, standard deviation, skewness, and kurtosis across speakers.
Speaker recognition using dynamic synapse-based neural networks with wavelet preprocessing
Authors: George Sageev , Berger Theodore
Published: October 2013

Two problems in the field of speaker recognition are noise robustness and low interspeaker variability. This project involved the design of a system that is capable of speaker verification on a closed set of speakers using a wavelet processing technique that allows for a speaker-dependent feature set extraction. Verification is accomplished using a dynamic synapse-based neural network with noise-resistance properties that is trained using a genetic algorithm technique. Using these techniques, the system was able to perform speaker verification without being adversely affected by normal levels of noise, and perform verification despite low variability between speakers.
Talker intelligibility: Child and adult listener performance
Authors: Markham Duncan , Hazan Valerie
Published: October 2013

In a study of talker intelligibility, 45 voices (adults, 11–12 year old children) were presented to 135 listeners (adults, 11–12, and 7–8 year olds). Word materials were presented in a ‘‘single-word’’ condition, and in a ‘‘triplet’’ condition, where a ‘‘normalizing’’ precursor sentence preceded three keywords. In both conditions, voices were randomized, with no consecutive presentations from the same speaker. The specially designed word-set consisted of 124 words chosen to maximize consonant confusions. Adult female speakers were significantly more intelligible than other groups, as predicted by previous research, but the difference was small. The error rates for 7–8 year olds were slightly but significantly higher than those for the older children and adults. The effect of presentation condition, however, was not significant for any listener group. Across all listener groups, rankings of speakers by error rates were strikingly consistent, with a distinct cluster of eight low-intelligibility speakers common to all listener groups. This suggests that speaker intelligibility is little influenced by listener-related factors. In terms of their perception of speaker characteristics, children aged seven and above are showing similar patterns of behavior to adults, even though the younger children showed marginally higher error rates. [Work funded by the Wellcome Trust.]
The relation between first-graders’ reading level and vowel production variability in real and nonsense words: A temporal analysis
Authors: Lydtin Kimberly , Fowler Anne , Bell-Berti Fredericka
Published: October 2013

The focus of this study is to determine if children who are poor readers produce vowels with greater variability than children with normal reading ability, since earlier research has indicated possible links between phonological difficulty, speech production variation, and reading problems. In continuation of our past research [K. Lydtin, A. Fowler, and F. Bell-Berti, J. Acoust. Soc. Am. 110, 2704 (2001)], where we looked at the spectral aspects of vowel production, we will report the results of our study of vowel duration and its variability in poor and good readers. The vowels chosen for this study are /ɪ/, /ε/, and /æ/ in real and nonsense words occurring in both blocked and random presentation. [Work supported by U.S. Dept. of Education, McNair Scholars Program.]
Specifying voicing differences in children’s productions of syllable-final stops: Knowledge versus skill
Authors: Nittrouer Susan
Published: October 2013

Among the acoustic correlates of phonetic identity considered to be universal is the length of vocalic segments preceding syllable-final stops, which is a correlate to the voicing of those stops. However, findings reported earlier [S. Nittrouer et al., J. Acoust. Soc. Am. 109, 2312(A) (2001)] showed that the commonly described length effect (i.e., shorter segments before voiceless than before voiced stops) is attenuated in adults’ samples from continuous discourse, and that listeners of all ages fail to make much use of this effect in perceptual decisions, preferring instead to base voicing judgments on dynamic spectral information. Subsequent to that study, acoustic measures (duration of the preceding vocalic segment and frequency of the first formant at voicing offset) of children’s (5 and 7 years of age) productions of words differing in the voicing of syllable-final stops showed that by 5 years of age children’s productions generally had the same acoustic structure as those of adults, but within-speaker variability on both measures was roughly twice as great in children’s as in adults’ productions. Thus, children were trying to coordinate the vocal-tract closing and glottal abduction gestures as adults do, but were not skilled enough to do so reliably. [Work supported by NIDCD.]
Reconstruction of normal velocity distribution at the face of an ultrasound source in liquid on the base of acoustic waveform measurements along a surface in front of the source
Authors: Sapozhnikov Oleg A. , Pishchalnikov Yuriy A. , Morozov Andrey V.
Published: October 2013

Normal velocity distribution along a vibrating surface is an important characteristic of any acoustic source. When it is known, the acoustic pressure field can be predicted using Rayleigh integral or similar approach. However, up to now there are no reliable methods of the velocity distribution measurement in liquids or solids. Due to strong acousto-optic interaction in condensed medium, the well-developed laser vibrometers can be employed only when the transducer is contacting vacuum or gas. In this work a novel method is developed and tested for evaluation of the velocity distribution along the vibrating surface of a piezoceramic transducer in liquid. The technique consists of measuring acoustic wave amplitude and phase along a surface surrounding the source, changing the sign of the phase, and theoretically backpropagating it to the source using the Rayleigh integral. The method was studied numerically and tested experimentally. The acoustic field of ultrasound source was registered using a needle hydrophone, which was scanned along a plane surface in front of the transducer. It is shown that the proposed approach enables accurate detection of the normal velocity. The method can be used for a wide variety of acoustically radiating structures. [Work supported by CRDF, NIH-Fogarty, and RFBR.]
Logic design and implementation of FPGA for a high frame rate ultrasound imaging system
Authors: Liu Anjun , Wang Jing , Lu Jian-yu
Published: October 2013

Recently, a method has been developed for high frame rate medical imaging [Jian-yu Lu, ‘‘2D and 3D high frame rate imaging with limited diffraction beams,’’ IEEE Trans. Ultrason. Ferroelectr. Freq. Control 44(4), 839–856 (1997)]. To realize this method, a complicated system [multiple-channel simultaneous data acquisition, large memory in each channel for storing up to 16 seconds of data at 40 MHz and 12-bit resolution, time-variable-gain (TGC) control, Doppler imaging, harmonic imaging, as well as coded transmissions] is designed. Due to the complexity of the system, field programmable gate array (FPGA) (Xilinx Spartn II) is used. In this presentation, the design and implementation of the FPGA for the system will be reported. This includes the synchronous dynamic random access memory (SDRAM) controller and other system controllers, time sharing for auto-refresh of SDRAMs to reduce peak power, transmission and imaging modality selections, ECG data acquisition and synchronization, 160 MHz delay locked loop (DLL) for accurate timing, and data transfer via either a parallel port or a PCI bus for post image processing. [Work supported in part by Grant 5RO1 HL60301 from NIH.]
Minor losses in oscillatory flow
Authors: Smith Barton L. , Swift Gregory W.
Published: October 2013

Energy dissipation that is manifested by gradients in pressure in a flow system is often expressed in terms of a pressure loss factor of the form K=Δ2P/ρv2. While there is a wealth of data on loss factors for a myriad of geometries in steady flow, little such data exists for pulsatile or oscillatory flow. Recent advances in thermoacoustics, which involves heat engines and refrigerators with no moving parts, motivate work in this area. An oscillatory flow system has been constructed to investigate loss factors in 2D geometries. The current results provide loss factors of entrances/sudden expansions. It is found that the losses are primarily a function of the displacement amplitude. The results also provide information on the variation of the ‘‘equivalent length’’ with the same parameter, and on turbulent dissipation in the channel. Oscillating flow in diffusers is also investigated, with emphasis on loss factors as a function of diffuser angle, and unsteady separation effects. [Work supported by the Los Alamos National Laboratory LDRD funds.]
Sediment interface and volume reverberation modeling with the parabolic approximation
Authors: Smith Kevin B. , Li Lit-Siew , Lee Boon-Chuan , Kao Han
Published: October 2013

A new reverberation model based on the parabolic approximation is developed that includes sediment interface and volume perturbations. A multiple forward/single backscatter approximation is made, and the structure of the solution is found to depend on the two-way propagation with a scattering strength scaling dependent on the local properties of the perturbation. The model is implemented for continuous wave (CW) signals to predict mean reverberation pressure levels and for broadband pulse signals to generate complex reverberation structures in the time-domain. The spatial correlation and statistical properties of these predicted signals are then analyzed in an attempt to extract information on the underlying characteristics of the perturbation. Preliminary analysis suggests that reverberation due to the volume perturbations decorrelates more rapidly over depth than the reverberation due to interface fluctuations, although the differences appear small. Additionally, the statistical character of the reverberation structure due to the interface appears as a relatively flat spectrum, while the spectrum of the volume reverberation tends to appear colored. Attempts to correlate these characteristics with the structure of the perturbations is ongoing. [Work supported by ONR, Code 321OA.]
Music technology and how it is being taught
Authors: Rossing Thomas D.
Published: October 2013

Music technology addresses techniques for creating, recording, and reproducing sound, constructing and repairing musical instruments, developing new and improved instruments, creating new sounds with computers, and scientific research to support these endeavors. Although rather well-defined music technology programs exist in other countries of the world, in the United States these techniques are generally taught in several different disciplines, and music technology is an interdisciplinary field of study. At our university, for example, students generally major in either physics or music but take courses in engineering and computer science as well. Attractive opportunities await students who gain a good background in musical acoustics and music.
Noisy offices for simple tasks and quiet offices for complex tasks?
Authors: Yoon Heakyung , Loftness Vivian
Published: October 2013

Many current office plans are designed as open environments to increase knowledge sharing, which is supposed to increase performance through more informal interactions between workers. However, according to workplace surveys, poor acoustics in open office environments have been reported to decrease workers performances. The literature regarding performance with quiet, ambient, and masking sound in offices show that the kinds of performed tasks in organizations or groups may be the main factor to decide whether open or closed office environments are appropriate. People engaged in simple office tasks perform better with masking sounds than with quiet or ambient office sound conditions [Loewen et al., ‘‘Cognitive and arousal effects of masking office noise,’’ Environment and Behavior 24, 381–395 (1992)]. However, when people need to use serial-recall functions in their complex tasks, quiet conditions may be better than other sound environments in offices [Banbury et al., ‘‘Disruption of office-related tasks by speech and office noise,’’ Br. J. Psychol. 499–517 (1998)].
Application of time reverse acoustics to acoustic measurements in a noisy environment
Authors: Park Sewon , Lauchle Gerald C.
Published: October 2013

For acoustic measurements made within noisy environments, time reversed acoustic methods can be used to improve the measurement. After reversing the array received time signal, rebroadcast of the reversed signals recreates the original source wave field at its original source location. In some measurement cases a background noise is created in the process of generating the source signal of interest; for example, wind and water tunnel acoustic experiments. By using time reverse acoustics, the signal-to-noise ratio can be improved. First, the source signal together with the background noise is recorded using an array of many reciprocal transducers. After the tunnel flow is stopped, the recorded signals are played in a time-reversed fashion through the reciprocal transducer elements of the array. If a receiver is located at the correct source location, only the source part of the rebroadcast signal is superimposed positively, with negligible influence from the background sources that originate elsewhere. Here, we describe noisy environment, free-field, time reversed acoustic simulations. The computer simulations show an improved signal-to-noise ratio. The advantages and disadvantages of using continuous or pulsed recorded signal are discussed. [Work supported by the Applied Research Laboratory E/F Program, and ONR, Code 333.]
Passive damping applications for noise and vibration reduction
Authors: Johnson Conor D. , Glaese Roger M. , Janzen Paul C.
Published: October 2013

This paper presents an overview of several unique techniques and their applications for passive damping for vibration and noise control. Most of the methods that are used target structural vibration and by its attenuation, transmitted acoustics as well. Viscoelastic materials are the most widely used technology for applications. An innovative family of viscoelastic materials, having fairly constant modulus and loss factor properties with respect to temperature, has recently been developed, with some materials in this family having very good thermal conductive properties as well. Another innovative viscoelastic method involves co-curing the viscoelastic and a composite host structure. Additionally, an innovative acoustic enclosure for precision manufacturing has been developed that relies on barrier mass and structural damping to attenuate acoustic transmission. Passive magnetic damping has been used in both tuned mass dampers and passive isolation systems for structural-acoustic systems. Research has been conducted on the design and applications of particle damping. By placing a number of small particles in a cavity of a vibrating structure, passive damping may be achieved over wide frequency and temperature ranges. The use of all of these methods will be illustrated through ground, air, and space-based examples.
Syntactic location facilitates word segmentation by infants
Authors: Johnson Elizabeth K. , Seidl Amanda , Jusczyk Peter W.
Published: October 2013

English learners begin to segment words and parse speech into prosodic units between 6 and 12 months. Recent experimental evidence suggests that segments are more fully realized at the edges of major syntactic constituents. For example, the [s] in ‘‘bass’’ will completely assimilate to [S] in the absence of a major syntactic boundary between the words ‘‘bass’’ and ‘‘shoppers.’’ In this study, we examine whether the location of words in a phrase (and hence the phonological strength of a word’s initial segment) affects infants’ segmentation. Eleven-month-olds were familiarized with stories containing the target words ‘‘acorn’’ and ‘‘shoppers,’’ using the head-turn preference procedure. For half of the infants, ‘‘shoppers’’ occurred after a major syntactic boundary, whereas ‘‘acorn’’ did not. For the other half, ‘‘acorn’’ occurred after a strong syntactic boundary, but ‘‘shoppers’’ did not. Infants in the first condition listened significantly longer to isolated versions of ‘‘shoppers’’ than to ‘‘acorn.’’ In contrast, infants in the second condition listened equally long to both familiar words. These findings suggest that words located at major syntactic boundaries are easier to segment. Our results also provide further evidence that infants’ segmentation of vowel-initial words is delayed compared to their segmentation of consonant-initial words.
Science of steelpans: What is known and what is not
Authors: Rossing Thomas D. , Hansen Uwe J.
Published: October 2013

One of the most important musical instruments developed in the 20th century is the Caribbean steelpan. In addition to being the foremost musical instrument in its home country of Trinidad and Tobago, the steelpan is becoming increasingly popular in North America and Europe. Scientific studies on the instrument have not kept pace with its growing popularity, however. This paper reviews some of the scientific studies that have been made on steelpans in our laboratory and elsewhere. One of the most important steps in understanding the steelpan is to understand how it vibrates and produces sound. We report measurements of modal shapes in different steelpans by prominent makers and attempt to interpret these results in terms of the geometry and fabrication history of these pans. We also discuss the physics of the material, including the residual stresses, the surface hardness, and the effect of heating.
Vibration of membrane excited by coupled acoustic energy from the bulk substrate
Authors: Guo Hang , Lal Amit
Published: October 2013

Vibration of a membrane is widely used in MEMS devices, such as membrane pumps for microfluidics and rf membrane switches. Conventionally, the membrane is excited by using interdigitated electrodes on piezoelectric ZnO thin films on the membrane. The small piezoelectric coefficient of ZnO limits the acoustic intensity for actuator application and membrane vibrate at one fixed frequency since the distance between interdigitated electrodes specifies the wavelength. In this paper, a novel cost-effective method to excite the membrane is proposed. A PZT plate is bonded to the bulk substrate and used to excite the membrane. The fundamental of this method is that the acoustic energy in the bulk substrate is coupled to the membrane for its vibration through the connecting boundary between the membrane and bulk substrate. Finite element method is used to calculate resonant frequencies and coupled acoustic energy, while the laser interferometer is used to verify resonant frequencies and mode shapes obtained from FEM and measure the actual displacement of the membrane in the air. The results show that for a 2 mm×2 mm×2.232 μm membrane, more than 30 membrane vibrations are obtained within the frequency up to 3 MHz, and the biggest membrane displacement is 0.27 μm, which is two times bigger than the conventional method.
Hyperbolic location errors due to insufficient numbers of receivers
Authors: Spiesberger John L.
Published: October 2013

Animal locations are sometimes estimated by measuring the difference in travel times of their sounds at pairs of receivers. Ideally, each difference specifies the animal’s location to a hyperboloid, and sufficient numbers of intersecting hyperboloids specify the location. Most bioacoustic publications state that one needs three receivers to locate animals in two spatial dimensions and four receivers in three spatial dimensions. However the actual numbers of receivers required for locations in two and three dimensions are four and five, respectively. Significant location errors can result from using insufficient numbers of receivers. Methods are provided for determining locations of ambiguous source-location regions.
Experimental study of a thermoacoustic electrical generator
Authors: Liu Jin , Spoor Philip S. , Corey John A. , Garrett Steven L.
Published: October 2013

The stack and heat exchangers from the historic Five Inch Engine [G. W. Swift, J. Acoust. Soc. Am. 92, 1551 (1992)] have been joined to a 2.02-m long resonator tube terminated by a variable acoustic load [A. M. Fusco et al., J. Acoust. Soc. Am. 91, 2229 (1992)]. Operation in 20-bar pure helium delivered 160 W to the load with an electrical heat input of 2.76 kW, producing a hot-end external duct temperature of 655°C. Applied heat measuring 1.41 kW was exhausted through the cold exchanger to a water stream at 25°C, with the remaining power producing useful work or otherwise lost by conduction through the engine and to the surroundings. Measured acoustic pressure amplitudes for electrical heat inputs in the range from 348 to 2773 W agreed with the deltae model to within 12%, but the error in the hot-end temperature prediction was 25%. The engine was then attached to a CFIC Model B-300 electrodynamic motor/alternator to explore feasibility of distributed power generation and co-generation. [The loan of the 5-in. engine, by G. W. Swift, Los Alamos National Laboratory, is gratefully acknowledged. J.L. and S.L.G. were supported, in part, by ONR.]
Contrastive focus in Beijing Mandarin
Authors: Chen Yiya
Published: October 2013

Contrastive focus in Beijing Mandarin. This study investigated the acoustic realization of contrastive focus in Beijing Mandarin. Here a contrastive focus is defined as a mechanism to signal contrast or make corrections in discourse. Two questions were asked. First, what are the acoustic cues employed to convey contrastive focus? Second, what are the linguistic constraints on the manifestation of prosodic cues? Four different renditions of each test sentence were elicited from the subjects with contrastive focus on different words to convey different pragmatic meanings. Preliminary results suggest: (1) All three acoustic cues under investigation F0, overall intensity, and duration are employed, with different degrees of consistency, to convey contrastive focus; (2) the manifestation of these cues also appear to be context sensitive. The implications of these phonetic facts for possible phonological organization of contrastive focus in Beijing Mandarin will be discussed. [Work supported by NSF Grant No. SBR 9600930 to Marie Huffman.]
Effects of speaking rate on temporal patterns of English
Authors: Smith Bruce L.
Published: October 2013

Previous research [B. L. Smith, J. Acoust. Soc. Am. 108, 2438–2442 (2000)] has indicated that individual subjects show considerable variation in the extent to which they manifest a number of temporal patterns in their speech (e.g., vowel lengthening before voiced obstruents, final-syllable vowel lengthening, etc.). At least in part, some of the variation across speakers was found to be related to the fact that some subjects naturally tend to talk somewhat faster/slower than others. The present study extended these previous findings concerning variations in temporal performance related to rate of speech by having 15 subjects produce several different CVC target stimuli in sentences spoken at both normal and fast rates. The temporal patterns observed as a function of these experimental manipulations of speaking rate generally supported the previous findings related to natural variations in rate of speech across subjects. It was found, for example, that vowel lengthening preceding voiced obstruents tended to be less when subjects spoke at a fast versus a normal rate. In contrast, phrase-final vowel lengthening was typically greater when subjects spoke at a faster rate. Possible reasons for these different vowel-lengthening effects may relate to the temporal domain that influences them.
Shock-free, forced oscillations of an air column in a closed tube
Authors: Sugimoto Nobumasa , Hashiguchi Takeshi , Masuda Mitsuhiro
Published: October 2013

This paper reports generation of high-amplitude, shock-free oscillations of an air column in a closed tube of uniform cross section. The air column is driven sinusoidally by the bellows mounted at one end of the tube at a frequency equal or close to the resonance frequency of the lowest mode. The shock-free oscillations are achieved by connecting an array of Helmholtz resonators to the tube axially. The array of resonators gives rise to wave dispersion, which changes the sound speed in this tube to depend on the frequency and makes the tube dissonant by avoiding coincidence of the higher-harmonic frequencies of excitation and the resonance ones of the higher modes. Each resonator is identical and small in a sense that the cavity’s volume is chosen much smaller than the tube’s volume per axial spacing between neighboring resonators, while the natural frequency of the resonator is chosen even higher than the lowest resonance frequency. Frequency response is obtained and compared with the theory up to the resonance frequency of the third mode. It is observed that the shock-free oscillations are realized at the sound pressure level of 170 dB where the shock would emerge unless the array were connected.
Focusing by spatiotemporal inverse filter: Application to heterogeneous and absorbing medium
Authors: Tanter Michael , Aubry J.-F. , Thomas J.-L. , Fink M.
Published: October 2013

In most applications of ultrasound, a first step consists in focusing a broadband ultrasonic beam deeply inside the medium. Nevertheless, sound speed, density, or absorption heterogeneities may strongly degrade the focusing. Different techniques have been developed to correct such aberrations (time reversal, speckle brightness,...). Recently, we investigated a new broadband focusing technique, the spatiotemporal inverse filter, based on the inversion of the propagation operator relating a transducer array to a set of control points inside the medium. As this inversion is achieved both in space and time, it allows one to calculate the set of temporal signals to be emitted by each array element for an optimal focusing on a chosen control point. Potential applications have been experimentally investigated in heterogeneous and absorbing media where classical geometrical focusing is highly degraded. The strong improvement achieved by inverse filter compared to time reversal and classical focusing emphasizes the great potential of multichannel systems having the ability to apply completely different waveforms on each element. Particularly, intraplate echoes suppression in NDT, high quality focusing through a human skull, as well as hyper-resolution in reverberating media highlight its great interest in various fields such as medical imaging, nondestructive testing, room acoustics, and underwater acoustics.
Probability of detection and false alarm for target signals measured with seafloor reverberation in a shallow water waveguide
Authors: Ratilal Purnima , Makris Nicholas C.
Published: October 2013

Probabilities of detection and false alarm are calculated as a function of the signal-to-diffuse-reverberation ratio for both deterministic and fluctuating targets in a variety of shallow water waveguides. The signal-to-diffuse-reverberation ratio is computed using the unified model [N. C. Makris and P. Ratilal, J. Acoust. Soc. Am. 109, 909–941 (2001)] for reverberation and submerged object scattering in a stratified medium. The reverberant background is range and azimuth dependent, and varies with the resolution footprint of the sonar system. Scenarios involving an active source and a horizontal receiving array are investigated. Predictions using this method are compared with data from the Geoclutter 2001 experiment. Detection and false alarm probabilities are calculated for submerged targets as well as geoclutter features in the shallow waters of the Stratafrom site off the coast of New Jersey. The results are consistent with our experimental findings that detection probabilities decrease with increasing range.
Spectrum of the time reversal operator
Authors: Chambers David , Gautesen A. K.
Published: October 2013

In a series of articles beginning in 1994, Prada and Fink showed that the behavior of any time reversal system could be determined by an analysis of a time reversal operator. This operator incorporates the effects of geometry, the background medium, and the scattering characteristics of objects within the medium. Initial analysis and experimental measurements for small, neutrally buoyant, point-like objects in a homogeneous medium showed a one-to-one correspondence between the eigenstates of the operator and individual scatterers. Recent work by Chambers and Gautesen for small spheres with arbitrary densities showed multiple eigenstates could exist for a single scatterer, breaking the one-to-one correspondence. In this talk, the spectral analysis of the time reversal operator is reviewed and new results are shown for compact scatterers of finite size and for an extended scatterer (a wire). It is shown that the number of eigenvalues for a given scatterer can be indefinitely large depending on the scattering physics. Furthermore, the spectrum for a collection of noninteracting objects is the combination of individual spectra from each scatterer. [Work performed under the auspices of the Department of Energy by the Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.]
Estimating Europa’s internal structure with ambient noise
Authors: Lee Sunwoong , Zanolin Michele , Thode Aaron M. , Makris Nicholas C.
Published: October 2013

Jupiter’s moon, Europa, is believed to possess a vast liquid ocean beneath a thin ice surface, although the thickness of the ice shell and depth of the ocean still remain poorly constrained. The authors have previously discussed the possibility of using ambient noise to probe Europa’s interior [Makris et al., Eos. Trans. Am. Geophys. Union 82(47), P22B-0552 (2001)]. Here the analysis is refined and extended. The probability density for high source level or ‘‘big bang’’ events from tidally induced surface cracks and meteor impacts is estimated. Such events are important because they are most likely to have returns from internal Europan strata that stand above the ambient noise level. Travel-time curves for various thicknesses are also presented and used to demonstrate that echo-sounding and tomographic techniques can be applied to estimate thickness of the ice layer, depth of the ocean, and internal temperature structure. Convective ice can also be detected by spectral analysis of surface waves, since significant contrast in shear wave speed is expected in the partial-melt-ice regime. Spectral analysis is also applied to analyze flexural modes of a thin ice shell, to estimate ice-shell thickness, and to potentially study the sediment layer on the seafloor.
Effects of an acoustic diode on lithotripter shock wave, cavitation, and stone fragmentation
Authors: Zhu Songlin , Dreyer Thomas , Liebler Marko , Zhong Pei
Published: October 2013

Recent studies suggest that reducing the large intraluminal bubble expansion in small blood vessels may ameliorate the potential for vascular injury in shock wave lithotripsy. To achieve this objective without compromising stone comminution, a selective truncation of the tensile component of lithotripter shock wave (LSW) is needed. In this work, an acoustic diode (AD) of Riedlinger’s design was constructed and evaluated. The AD consists of two peripherally secured membranes having opposite surfaces held in direct contact under partial vacuum. The AD permits transmission of the leading compressive component of a LSW; yet the membranes may separate under tension, thus blocking the transmission of the trailing tensile component of the LSW. Following each LSW, the membranes will again establish direct contact due to the partial vacuum between them. Using the AD at a vacuum level of 10.75 in.Hg, the collapse time of the LSW-induced bubble cluster at the beam focus of a HM-3 lithotripter at 20 kV was found to be reduced by 29%, whereas the compressive pressure and stone comminution were only reduced slightly by 4% and 5%, respectively. Thus the AD may be used to reduce tissue injury produced by LSW. [Work supported by Whitaker Foundation and NIH.]
Effectiveness of using time reverse signal processing for mitigating multipath in communications channels
Authors: Meyer Alan W. , Candy James V. , Poggio Andrew J.
Published: October 2013

The use of time reverse signal processing (TRSP) to compensate for distortion in a communications channel is well established in recent literature. Our recent work quantifies the effectiveness of TRSP techniques vis-à-vis traditional adaptive equalization techniques. These quantitative measurements are developed using simulations and laboratory experiments. A rigorous mathematical development of the communications problem is first necessary to establish a consistent model of the communications channel, and various approaches for implementing TRSP and adaptive equalization as well. These techniques are then simulated and performance measures developed for a large set of conditions spanning an increasing number of multipaths and increasing SNR. Acoustic laboratory experiments are also conducted in a highly reverberant environment to confirm both our techniques and results. In this paper we report on these measures of effectiveness comparing TRSP vis-a-vis traditional adaptive equalization techniques for compensating for multipath in a communications channel. [Work performed under the auspices of the Department of Energy by the Lawrence Livermore National Laboratory under contract W-7405-Eng-48.]
New calculation strategy for acoustic radiation from a thick annular disk
Authors: Lee Hyeongill , Singh Rajendra
Published: October 2013

This article proposes a new semianalytical procedure for the calculation of sound radiation from a thick annular disk when it is excited by arbitrary harmonic forces. As the first step, structural eigensolutions for both in-plane (radial) and out-of-plane (flexural) modes are calculated using analytical methods. These are examined by the finite element analyses as well as the experimental investigations. The far-field sound pressure distributions (including directivity) due to selected modes of the disk are obtained from numerically obtained surface velocities using Rayleigh integral solutions based on cylindrical or circular plate radiator formulations. Such formulations define the modal radiation solutions corresponding to the structural eigensolutions of a thick disk. The boundary element analyses and vibro-acoustic experiments validate analytical predictions. Surface velocity and far-field sound pressure due to an arbitrary harmonic force excitation are then obtained from the structural and acoustic normal mode expansions. Based on the far-field sound pressure, acoustic power and radiation efficiency spectra are obtained. The method is also confirmed by comparing analytical results with those from finite and boundary element analyses. Finally, the effect of coupling between modes is also investigated by the proposed procedure.
An acoustical study of English word stress produced by Americans and Koreans
Authors: Yang Byunggon
Published: October 2013

Acoustical correlates of stress can be divided into duration, intensity, and fundamental frequency. This study examined the acoustical difference in the first two syllables of stressed English words produced by ten American and Korean speakers. The Korean subjects scored very high in TOEFL. They read, at a normal speed, a fable from which the acoustical parameters of eight words were analyzed. In order to make the data comparison meaningful, each parameter was collected at 100 dynamic time points proportional to the total duration of the two syllables. Then, the ratio of the parameter sum of the first rime to that of the second rime was calculated to determine the relative prominence of the syllables. Results showed that the durations of the first two syllables were almost comparable between the Americans and Koreans. However, statistically significant differences showed up in the diphthong pronunciations and in the words with the second syllable stressed. Also, remarkably high r-squared values were found between pairs of the three acoustical parameters, which suggests that either one or a combination of two or more parameters may account for the prominence of a syllable within a word. [Work supported by Korea Science Foundation R01-1999-00229.]
Auditory feature detection for stimuli presented from different directions
Authors: Bronkhorst Adelbert W. , Townsend James T.
Published: October 2013

The processing of stimulus features by the visual system is commonly studied by measuring response times (RTs) for detection of targets presented with a varying number of distracters. In audition, however, interpretation of the interaction between target and distracters is complicated by effects like masking, binaural gain and fusion. In the present paradigm, which uses stimuli presented from different directions in the horizontal plane, these confounding effects were either minimized or kept constant. Targets were synthetic vowels and RTs were measured for detection of three features: F0, spectrum (type of vowel) and direction. Both single features and conjunctions were studied. Independent variables were the type of distracters (synthetic vowels or spectrally shaped noise) and their number. Results show that the effect of the number of distracters on the RT is smallest for the spectrum feature; RTs for the detection of F0 are largest and vary considerably across subjects. For conjunctions of features, the RTs lie, as expected, between the RTs for the single features. The effect of the type of distracter on the RT is small—this indicates that the processing involved in segregating vowels from noise is not more efficient than that used for segregating vowels from other vowels.
The direct-to-reverberant ratio as cue for distance perception in rooms
Authors: Bronkhorst Adelbert W. , Zahorik Pavel
Published: October 2013

Although it is evident that in order to localize a sound source, one has to perceive both its direction and its distance, localization research has for many years focused mainly on the directional component. This situation has changed in the last few years. Recent studies have provided more insight into distance perception and the specific cues that are used by the auditory system. It appears that auditory and visual distance perception are similar, because both rely on a combination of cues, which are weighted differently in different environments. One auditory cue that has received particular attention is the direct-to-reverberant energy (D/R) ratio, because it is thought to be relatively stable, particularly in rooms. At present, however, it is not clear what the precise contribution of this cue is or how it is coded in the auditory system. Evidence that the cue is derived from the monaural time-domain signal is contradicted by other data suggesting that it relies on binaural information. Furthermore, direct measurement of JNDs for the D/R ratio reveals unexpectedly poor performance. Merging these seemingly incompatible results into a coherent model is challenging, but necessary for obtaining a clearer picture of how the D/R cue contributes to perceived distance.
Inversion of shallow water ocean acoustic data using a complex plane-wave reflection coefficient approach
Authors: Stotts Steven , Knobles David , Koch Robert , Cook Adam , Grant David , Focke Karl
Published: October 2013

A previously reported method of inversion in range-dependent environments using a complex plane-wave approach [Stotts et al., J. Acoust. Soc. Am. 109, 2334 (2001)] has been applied to data analysis. The method separates the propagation in the water column from the interaction with the seabed by first calculating and then storing the eigenray characteristics associated with the assumed known waveguide geometry. The inversion is then performed by calculating the plane-wave reflection coefficients at the predetermined angles and constructing the modeled field of the entire propagation for each perturbation of the seabed parameters. Results of applications of this model to data taken off the coast of Florida during the spring of 2001, will be presented. Consistent inversion results obtained from other models along with an examination of received time series, as well as sound speed profiles collected over the region, will also be discussed in the context of range-dependent inversion analysis. Comparisons of this method to a direct reflection coefficient inversion approach provide insight into the use of reflection coefficients as an inversion product.
Transposed stimuli improve sensitivity to envelope-based interaural timing information for stimuli having center frequencies of up to 10 kHz
Authors: Bernstein Leslie R. , Trahiotis Constantine
Published: October 2013

Threshold interaural temporal disparities (ITDs) at high frequencies are larger than threshold ITDs obtained at low frequencies. Colburn and Esquissaud [J. Acoust. Soc. Am. Suppl. 1 59, S23 (1976)], hypothesized that this reflects differences in peripheral processing of the stimuli rather than in binaural mechanisms that mediate performance. Previously [L. R. Bernstein and C. Trahiotis, J. Acoust. Soc. Am. 109, 2485 (2001)] this hypothesis was supported in ITD-discrimination experiments employing high-frequency ‘‘transposed stimuli’’ centered at 4 kHz that were designed to provide high-frequency channels with envelope-based information mimicking that normally available only in low-frequency channels. Here, we report new results using stimuli centered at 4, 6, and 10 kHz. It was found that (1) transposed stimuli can yield relatively small threshold ITDs, even at 6 and 10 kHz, (2) the data could be well accounted for in terms of a constant-criterion change in normalized interaural correlation computed subsequent to bandpass filtering, compression, rectification, and low-pass filtering. In addition, it was found necessary to incorporate a specific limitation to capture the inability of the auditory system to follow envelope fluctuations greater than 150 Hz. [Work supported by NIH DC 04147.]