Amplitude Dip Research Articles

Analysis of Tapered Fibre Optic Surface Plasmon Resonance Bio-Sensor Chip With Highly Perturbed Taper Profiles.

A numerical model based on the Transfer matrix method (TMM) is proposed for the first time to study the gold coated tapered fibre optic surface plasmon resonance (SPR) with eight different types of taper profiles namely linear, exponential-linear, Gaussian, quadratic, sinusoidal, error function type and highly perturbed taper profile so-called chirp type of profile. The performance in terms of sensitivity, full width at half maximum (FWHM), detection accuracy (D.A.), amplitude dip, and half power points are estimated with respect to tapering ratio and choices of taper profile. It is found that sensitivity increased almost linearly with the taper ratio of each taper choice for the account of the reduction of detection accuracy. It has been found that sensitivity is highest for the case of chirp taper profile and lowest for the case of quadratic taper profile at low taper ratio. In this study, the aqueous solution is considered for sensor development which is adulterated by biomolecules species like DNA, blood samples, etc.

Acoustics of the creaky phonations in Yateé Zapotec

Yateé Zapotec (YZ) is a variety of Zapotec spoken in San Francisco Yateé, Oaxaca, Mexico. The language has three phonation types: modal, checked, and rearticulated. Checked and rearticulated phonations both involve glottalization realized on vowels but differ in the phasing of the glottalization in vowels. Checked phonation has late-phased glottalization whereas rearticulated phonation is characterized by mid-phased glottalization. Previous studies on the phonetics of Zapotec phonations seldom compare the phonations in the time domain. In this study, we compare the spectral tilt, degree of noise, amplitude of voicing, and duration of the three phonations over the time course of vowels. Using multi-dimensional scaling analysis, we also find that the amplitude dip in the middle of the vowels (induced by glottalization) differentiates rearticulated vowels from modal and checked vowels, while the shorter duration differentiates checked vowels from modal and rearticulated vowels. We conclude that in YZ, mid-phased glottalization is the defining feature of rearticulated phonation whereas duration is the defining feature of checked vowels. Future studies can test whether YZ listeners are also more sensitive to amplitude dip and short duration when perceiving rearticulated and checked vowels.

Glimpsing speech interrupted by speech-modulated noise

Everyday environments frequently present speech in modulated noise backgrounds, such as from a competing talker. Under such conditions, temporal glimpses of speech may be preserved at favorable signal-to-noise ratios during the amplitude dips of the masker. Speech recognition is determined, in part, by these speech glimpses. However, properties of the noise when it dominates the speech may also be important. This study interrupted speech to provide either high-intensity or low-intensity speech glimpses derived from measurements of speech-on-speech masking. These interrupted intervals were deleted and subsequently filled by steady-state noise or one of four different types of noise amplitude modulated by the same or different sentence. Noise was presented at two different levels. Interruption by silence was also examined. Speech recognition was best with high-intensity glimpses and improved when the noise was modulated by missing high-intensity segments. Additional noise conditions detailed significant interactions between the noise level and glimpsed speech level. Overall, high-intensity speech segments, and the amplitude modulation (AM) of the segments, are crucial for speech recognition. Speech recognition is further influenced by the properties of the competing noise (i.e., level and AM) which interact with the glimpsed speech level. Acoustic properties of both speech-dominated and noise-dominated intervals of speech-noise mixtures determine speech recognition.

Active modulation of the terahertz spectra radiated from two air plasmas.

A simple and energy-saving method has been proposed to actively modulate the spectra of terahertz (THz) waves radiated from two serial plasmas, which uses the background light to generate one plasma to make full use of the energy of the femtosecond laser. With this method, the modulation of the central frequency, spectral bandwidth, and spectral profile of the output THz waves have been observed. The shifting of the amplitude dip has been manipulated by changing the distance of the two serial plasmas. The manipulation results agree with the ones simulated by the transition-Cherenkov model. This proposed method provides a useful tool for getting the modulated THz spectra that can be used in the THz remote sensing.

The OmegaWhite survey for short-period variable stars – III: follow-up photometric and spectroscopic observations

We present photometric and spectroscopic follow-up observations of short-period variables discovered in the OmegaWhite survey: a wide-field high-cadence g-band synoptic survey targeting the Galactic Plane. We have used fast photometry on the SAAO 1.0-m and 1.9-m telescopes to obtain light curves of 27 variables, and use these results to validate the period and amplitude estimates from the OmegaWhite processing pipeline. Furthermore, 57 sources (44 unique, 13 also with new light curves) were selected for spectroscopic follow-up using either the SAAO 1.9-m telescope or the Southern African Large Telescope. We find many of these variables have spectra which are consistent with being delta Scuti type pulsating stars. At higher amplitudes, we detect four possible pulsating white dwarf/subdwarf sources and an eclipsing cataclysmic variable. Due to their rarity, these targets are ideal candidates for detailed follow-up studies. From spectroscopy, we confirm the symbiotic binary star nature of two variables identified as such in the SIMBAD database. We also report what could possibly be the first detection of the `Bump Cepheid' phenomena in a delta Scuti star, with OW J175848.21-271653.7 showing a pronounced 22% amplitude dip lasting 3 minutes during each pulsational cycle peak. However, the precise nature of this target is still uncertain as it exhibits the spectral features of a B-type star.

Glottalization, reduction, and acoustic variability in function words in American English

Function words vary widely in pronunciation; understanding this variation is essential for accurate cognitive modeling of lexical perception and production, as well as for computer speech applications. This study analyzed acoustic variation in pronunciation of vowel-initial words a, are, our, and or, as well as her, which has a vowel-initial variant, [ɚ]. Sentences were constructed in which each function word was preceded by a phonetically similar open syllable rhyme, with which the word was expected to sometimes blend spectrally. Twenty-nine participants uttered 100 sentences in a casual speaking style. The degree of clarity of function word onsets was measured, focusing on evidence of onset discontinuities: glottal onset gestures (e.g., low fundamental frequency, F0; amplitude dips) for vowel-initial words a, are, our, and or, and, for her, of /h/ (e.g., root-mean-square amplitude, amplitude differences of first and second harmonics). Results showed that a substantial proportion of the time, function words lacked any detectable acoustic onset discontinuity. When discontinuities did occur before vowel-onset function words, there was a high degree of acoustic variability in those realizations. These findings highlight the challenges for speech perception to identify word onsets and/or to overcome variability in recognizing words. [Work supported by NSF Grant BCS-1431063.]

Modulation masking and glimpsing of natural and vocoded speech during single-talker modulated noise: Effect of the modulation spectrum.

Compared to notionally steady-state noise, modulated maskers provide a perceptual benefit for speech recognition, in part due to preserved speech information during the amplitude dips of the masker. However, overlap in the modulation spectrum between the target speech and the competing modulated masker may potentially result in modulation masking, and thereby offset the release from energetic masking. The current study investigated masking release provided by single-talker modulated noise. The overlap in the modulation spectra of the target speech and the modulated noise masker was varied through time compression or expansion of the competing masker. Younger normal hearing adults listened to sentences that were unprocessed or noise vocoded to primarily limit speech recognition to the preserved temporal envelope cues. For unprocessed speech, results demonstrated improved performance with masker modulation spectrum shifted up or down compared to the target modulation spectrum, except for the most extreme time expansion. For vocoded speech, significant masking release was observed with the slowest masker rate. Perceptual results combined with acoustic analyses of the preserved glimpses of the target speech suggest contributions of modulation masking and cognitive-linguistic processing as factors contributing to performance.

Ultrafast gain recovery in a QW-SOA and its application for 40 Gb/s regenerative format conversion from NRZ-DPSK to RZ-OOK

We propose a scheme to realize gain recovery of the order of a few picoseconds in a typical quantum well semiconductor optical amplifier (QW-SOA) using a pump signal with amplitude dips. In the scheme, the gain recovery is determined by the fast carrier density depletion and carrier temperature heating processes. The ultrafast gain recovery is numerically verified by a completed model combining the QW band structure calculation with rate equations in the QW-SOA. In practice, a pump signal with amplitude dips can be partly characterized by a non-return-to-zero differential phase-shift keying (NRZ-DPSK) signal generated by a Mach–Zehnder modulator. Therefore, we experimentally demonstrate 40 Gb/s wavelength-converting and regenerative format conversion from NRZ-DPSK to return-to-zero on–off keying (RZ-OOK), which may be a key function to connect different kinds of modulation formats at gateway nodes between long-haul backbone networks and metro area networks.

Linear cochlear mechanics.

An active, three-dimensional, short-wavelength model of cochlear mechanics is derived from an older, one-dimensional, long-wavelength model containing time-delay forces. Remarkably, the long-wavelength model with nonlocal temporal interactions behaves like a short-wavelength model with instantaneous interactions. The cochlear oscillators are driven both by the pressure and its time derivative, the latter presumably a proxy for forces contributed by outer hair cells. The admittance in the short-wavelength region is used to find an integral representation of the transfer function valid for all wavelengths. There are only two free parameters: the pole position in the complex frequency plane of the admittance, and the slope of the transfer-function phase at low frequencies. The new model predicts a dip in amplitude and a corresponding rapid drop in phase, past the peak of the traveling wave. Linear models may be compared by their wavelengths, and if they have the same dimension, by the singularity structure of their admittances.

Range of variability in native and non-native spontaneous speech intervocalic stops

Speakers produce sounds differently in spontaneous vs careful speech, and how they do this shows both similarities and differences across languages. The current project examines spontaneous conversational speech and read speech among monolingual English speakers, Dutch-English bilinguals, and Spanish-English bilinguals (for Dutch and Spanish, in both their L1 and English). The phonology of intervocalic stops differs in these languages: Dutch has final devoicing, Spanish has approximation of /bdg/, and English has flapping of /td/. In our recordings, Dutch speakers often devoiced final stops in both Dutch and English in spontaneous speech, while native English speakers produced voiced stops or approximants. Speakers of all the languages produced some approximant realizations and some deletions. Through measurements of consonant duration, amplitude dip during the consonant, and cessation of voicing, this work shows the range of acoustic variability produced by speakers of three languages in their L1 and their L2, in spontaneous and careful speech. This allows a comparison of how much of speech variability stems from the native language phonology, from language-specific phonetics, and from language-general spontaneous speech reduction.

Amplitude-mediated chimera states

We investigate the possibility of obtaining chimera state solutions of the nonlocal complex Ginzburg-Landau equation (NLCGLE) in the strong coupling limit when it is important to retain amplitude variations. Our numerical studies reveal the existence of a variety of amplitude-mediated chimera states (including stationary and nonstationary two-cluster chimera states) that display intermittent emergence and decay of amplitude dips in their phase incoherent regions. The existence regions of the single-cluster chimera state and both types of two-cluster chimera states are mapped numerically in the parameter space of C(1) and C(2), the linear and nonlinear dispersion coefficients, respectively, of the NLCGLE. They represent a new domain of dynamical behavior in the well-explored rich phase diagram of this system. The amplitude-mediated chimera states may find useful applications in understanding spatiotemporal patterns found in fluid flow experiments and other strongly coupled systems.

Direct Observation of Large Quantum Interference Effect in Anthraquinone Solid-State Junctions

Quantum interference in cross-conjugated molecules embedded in solid-state devices was investigated by direct current-voltage and differential conductance transport measurements of anthraquinone (AQ)-based large area planar junctions. A thin film of AQ was grafted covalently on the junction base electrode by diazonium electroreduction, while the counter electrode was directly evaporated on top of the molecular layer. Our technique provides direct evidence of a large quantum interference effect in multiple CMOS compatible planar junctions. The quantum interference is manifested by a pronounced dip in the differential conductance close to zero voltage bias. The experimental signature is well developed at low temperature (4 K), showing a large amplitude dip with a minimum >2 orders of magnitude lower than the conductance at higher bias and is still clearly evident at room temperature. A temperature analysis of the conductance curves revealed that electron-phonon coupling is the principal decoherence mechanism causing large conductance oscillations at low temperature.

Clinical Use of a One Hertz Bin Electroencephalography Assessment to Distinguish Elite from Less Elite and Typical from Atypical Athlete Profiles

The purpose of this paper was to highlight preliminary research into the use of one electroencephalography (EEG) site (Cz) and 1 Hz bins to identify elite athletes during the assessment process. Eyes-open baseline data from several small groups of athletes (tennis, gymnastics) suggest that elite athletes have a dip in amplitude in very low frequencies and then an increased amplitude at 10 Hz in a single-site EEG spectral display, when compared with less successful teammates. Other clinical sites and research labs will need to replicate the reliability and value of this pattern. Three case studies demonstrate the potential for clinicians to use EEG information analyzed in 1 Hz bins to identify areas for clinical exploration. The authors suggest that the presentation of EEG data related to possible emotional issues makes it possible to discuss more quickly and directly any potential problem areas for athletes.

Acoustic articulatory evidence for quantal vowel categories: The feature [low

The goal of this study is to determine whether acoustic coupling between the first subglottal resonance F1sub (about 600 Hz) and the F1 frequency for vowels creates a region near 600 Hz in which the F1 prominence shows an irregularity. Such a finding would provide evidence for a defining quantal articulatory-acoustic relation for the distinctive feature [low]. The time course of F1 in relation to F1sub was examined for certain diphthongs and several monophthongs produced by a number of speakers of English using Chi’s data [X. Chi and M. Sonderegger, J. Acoust. Soc. Am. 115, 2540–2550 (2004)]. For the diphthongs, a discontinuity in F1 or a dip in amplitude of the F1 prominence was observed as it passed through F1sub, while for the monophthongs, F1 was usually above F1sub for [+low] vowels and below F1sub for [-low] vowels. A preliminary further study of data from the literature on F1 for vowels from various languages showed that the boundary between F1 values of [+low] vowels and those of [-low] vowels agrees with the average value of F1sub obtained from the laboratory study with English. [Supported by NIH Grant No. DC00075.]

Investigations of Coherent Vibrational Oscillations in Myoglobin

The technique of femtosecond coherence spectroscopy (FCS) is applied to the heme protein myoglobin. Photostable samples of deoxy myoglobin (Mb) and photochemically active samples of the nitric oxide adduct (MbNO) are investigated. The pump-induced change in the probe transmittance for both samples displays coherent oscillations that, when transformed into the frequency domain, are in agreement with the resonance Raman spectrum of deoxy Mb. This indicates that the coherences associated with the photoreactive sample (MbNO) arise from the rapidly changing forces appearing in the crossing region(s) between the reactant and product state potential energy surfaces. The relative phase and amplitude of the Fe−His vibration, associated with the sole covalent linkage between the heme and the protein, are analyzed as a function of sample state and pump/probe carrier frequency. The dependence of the phase on carrier frequency is found to be significantly different for the “field driven” coherence in Mb and the “reaction driven” coherence in MbNO. In MbNO we observe a dip in amplitude and a phase flip near 439 nm for the Fe−His mode, whereas in deoxy Mb we observe a nearly constant phase and amplitude for this mode across the Soret absorption band. These observations are shown to be in good agreement with a simple theoretical model of the pump−probe experiment. Finally, we present recent observations of strong low-frequency oscillations, occurring near 40 cm-1 in both species and near 80 cm-1 for MbNO.

An Economical Touch Panel Using SAW Absorption

Surface waves are readily absorbed when a soft object such as a fingertip touches the substrate. This familiar observation is put to use in a touch-sensing display panel to provide readouts of finger location and finger pressure. Reflective array strips placed a long the panel edges s urround the entire panel area. A short pulse launched, say, along the top edge from left to right arrives at the bottom left corner having a long rectangular envelope, w ith each point in time corresponding to a specific vertical path across t he panel. A finger touch causes an amplitude dip whose timing and depth indicate location and finger pressure. Low frequencies (4-10 MHz) make low-cost arrays p ractical. Signal/noise ratio is very high, so the c enter of the dip can be located precisely; r esolution is determined by the associated digital circuits.

Automatic recognition of intervocalic voiced stops

The recognition accuracy for intervocalic voiced plosives using a simple consonant detector combined with a context‐dependent Bayesian classifier was studied. The consonantal segments were located by running a dip detector over the smoothed log‐energy contour. The vocalic nuclei were located at the segments of least spectral change. LPC spectra along the vocalic segments were the features for their classification which was performed by a compound Bayes decision procedure. The feature set for the Bayesian context‐dependent classification of voiced stop sounds was a sequence of three selected LPC spectra located along the amplitude dip. One spectrum was obtained at the point of minimal energy and the other two were obtained at the points of maximum slope of the smoothed log‐energy contour at the beginning and end of the consonantal segment. A recognition performance of 92% was obtained in a speaker‐dependent manner using a database consisting of nearly 1300 consonants embedded in VCVCVCV nonsense sequences where the V's were the vowels /a,i,u/ and the C's were the voiced stops /b,d,g/ uttered by two male Argentine Spanish speakers.

Analysis of performed transitions in orchestral instruments

The region between performed notes was examined in nine instruments (flute, bass flute, piccolo, clarinet, oboe, bassoon, trumpet, violin, and cello). On each instrument, eight intervals (2nd, 3rd, 5th, 7th, ascending, and descending) and two playing styles (tongued/untongued, bow change/no bow change) were digitally recorded. Using a computer, the recordings were analyzed for time‐varying power and time‐varying spectrum (phase vocoder). Analysis of as many as five recordings of a given interval and playing style showed that the performer could easily replicate a given transition, so the recordings were judged as representative. In the tongued (bow change) case, the notes were farther apart, the amplitude dip between the notes (except in the cello) was greater, and spectral changes were more extensive than in the nontongued (no bow change) case. This pattern was not significantly influenced by variation in the size of the interval, the direction of the interval, or the instrument performing. [Work perform...

Test of an automatic syllable peak detector

It is a venerable and commonplace intuition that syllables are “peaks of sonority.” Previous work by Mermelstein [J. Acoust. Soc. Am. 58, 880–883 (1975)] suggests that this intuition is nearly true on the acoustic surface of speech, and that relatively crude algorithms based on amplitude variation can work fairly well at counting syllables and locating their approximate extent. We have devised a simple speaker‐independent algorithm for detecting sonority peaks in continuous speech, and tested its accuracy as a syllable finder on several paragraphs of casual reading by four speakers. Performance was encouraging: less than 10% misses, and less than 1% false triggers. The misses were about evenly divided among (1) vowel‐vowel transition, where no sonority minimum is expected, (2) intervocalic sonorants with insufficient amplitude dip, and (3) devoiced or deleted schwas. Methods for dealing with these cases will be discussed.

The C-wave of the rabbit electroretinogram during dark-adaptation and the steady-state.

C-waves of the rabbit ERF under urethane anesthesia were elicited by a Grass photostimulator during dark adaptation and under steady-state conditions. After strong pre-adaptation with light, the amplitude and time-to-peak of the c-wave increased in parallel with the a- and b-waves, reaching a maximum of 90-130 min. In the dark-adapted steady-state, repetitive stimuli at intervals ranging from 15 sec to 5 min elicited a stable c-wave response except for a small dip in amplitude that occurred 2-6 min after initiating the shortest interval (15 sec) flashes. Although the changes in light and dark used in these experiments should have elicited shifts in the standing potential, no fluctuations of the c-wave amplitude were evident with a time course corresponding to a light response of the standing potential.