Repetitive Signals Research Articles

Distinguishing FM‐modulated bowhead whale calls from airgun and other biologic signals using image processing, feature extraction, and neural networks.

The detection and identification of repetitive or stereotyped bioacoustic signals in raw acoustic data are typically accomplished via matched filtering or spectrogram correlation techniques. However, the detection of FM‐modulated sweeps that have variable frequency‐modulated contours or bandwidths is still an active challenge. The problem is made more complex by the possible presence of other frequency‐modulated signals such as airguns or other biologics. To provide a specific example, in 2007 and 2008 directional autonomous recording packages (DASARs) were deployed in the Beaufort Sea to monitor the annual migration of the bowhead whale (Balaena mysticetus) population during seismic exploration activities. A portion of these data sets has been manually analyzed, providing an opportunity to characterize the miss and false alarm rates of various FM‐modulated detection and classification methods. Here literature and software on bioacoustic FM‐contour tracing and classification are reviewed, with a particula...

Time stretch enhanced recording oscilloscope

Recording analog signals using photonic time-stretch technique in a mode which combines advantages of continuous signal capture, as in real-time analog-to-digital converters (ADCs), and very high bandwidth capability of (equivalent-time) sampling oscilloscopes, is proposed. It is shown that the eye diagrams of high speed serial data can be acquired at least 100 times faster than the fastest capture rates today. Unlike conventional sampling scopes, this technique can capture ultrafast dynamics of repetitive signals, nonrepetitive signals, and rare events. Experimentally, 45 Gbit/s data eye diagram measurement is demonstrated.

The effect of repeated vibration signals on worker behavior in established and newly founded colonies of the honey bee, Apis mellifera

Communication signals used in animal social interactions are frequently performed repetitively, but the function of this repetition is often not well understood. We examined the effects of signal repetition by investigating the behavior of worker honey bees that received differing numbers of vibration signals in established and newly founded colonies, which could use signal repetition differently to help adjust task allocations to the labor demands associated with the different stages of colony development. In both colony types, more than half of all monitored workers received more than one vibration signal, and approximately 12% received ≥5 signals during a given 20-min observation period. Vibrated recipients exhibited greater activity and task performance than same-age non-vibrated controls at all levels of signal activity. However, vibrated workers showed similar levels of task performance, movement rates, cell inspection rates, and trophallactic exchanges regardless of the number of signals received. Thus, the repeated performance of vibration signals on individual bees did not cause cumulative increases in the activity of certain workers, but rather may have functioned to maintain relatively constant levels of activity and task performance among groups of recipients. The established and newly founded colonies did not differ in the extent to which individual workers received the different numbers of vibration signals or in the levels of activity stimulated by repeated signals. Previous work has suggested that compared to established colonies, newly founded colonies have a greater number of vibrators that perform signals on a greater proportion of the workers they contact. Taken in concert, these results suggest that vibration signal repetition may help to adjust task allocations to the different stages of colony development by helping to maintain similar levels of activity among a greater total number of recipients, rather than by eliciting cumulative effects that cause certain recipients to work harder than others.

The impact of repetition-induced familiarity on agreement with weak and strong arguments.

Repeated statements are perceived as more valid than novel ones, termed the illusion of truth effect, presumably because repetition imbues the statement with familiarity. In 3 studies, the authors examined the conditions under which and the processes by which familiarity signals from repetition and argument quality signals from processing of message content influenced agreement with persuasive arguments. Participants with low or high motivation to process information were presented persuasive arguments seen once or twice. In all 3 studies, repetition increased the persuasiveness of weak and strong arguments when little processing of message content occurred. Two of the studies used a process dissociation procedure to reveal that both greater controlled processing (which reflected argument content) and the greater automatic influence of familiarity (which reflected repetition) were associated with increased acceptance of strong arguments but that greater controlled processing dissipated the benefits of familiarity for agreement with weak arguments.

Seismic Raves: Tremor Observations from an Electronic Dance Music Festival

Repetitive signals of sustained amplitude are observed both in music and seismology; in music this is often described as the rhythm, whereas in seismology such signals are often labeled as tremor ( e.g. , Chouet 1996). Tremor is generated by a variety of sources including volcanoes, glaciers, and hydroelectric plants (for examples, see Ferrick et al. 1982) and is often characterized by narrowband spectral features that maintain their amplitude, sometimes for periods of hours or days (so-called harmonic tremor). In this paper we present observations from an unusual anthropogenic source of seismic tremor, generated at an interface between music and seismology: an electronic dance music festival. Music festivals, popular in the summer months across the United Kingdom, provide a meeting point for thousands of enthusiasts to listen to live music. Many of these festivals concentrate on a particular genre of music; e.g. , dance, folk, rock, or world. Previously observed vibrations from rock music festivals have been attributed to large crowds in confined spaces jumping up and down in time to the music, although seismograms were not recorded (Erlingsson and Bodare 1996; Browitt and Walker 1993). Electronic dance music, characterized by strong repetitive rhythms, is the focus for the Glade electronic dance music festival that has been held in the Berkshire countryside for one weekend a year from 2004 to 2007 (see figure 1). The festival consists of a number of music stages and tents, each of which specializes in particular subgenres of electronic dance music. In 2007, approximately 8,500 people enjoyed the festival over the weekend of 20–22 July. To amplify the music to a level suitable for an outdoor concert, the power output of the public address (PA) systems ranged from 2 to 26 kW; the loudspeakers are powerful acoustic sources that are coupled into the ground …

Acoustic emissions for the prediction of avalanches

Although we know well enough the main zones where occur avalanches, the main difficulty results in forecasting avalanches because of the constant evolution of the snow coat. The coat, composed of various slopes have different properties according to the weather conditions not only during falls but also after. Weather modifications after snow falls generate instability of slopes which create stress, fissure and failure states. These different states generate acoustic emissions whose parameters can lead to forecast avalanches. The aim is to detect in situ these precursors, that initiate a low frequency signal. We have settled an experiment to monitor and register this signal. It includes two geophones to detect the acoustic signals, an acquisition system, one aerial of temperature sensor and a wireless connection to a deported PC. The system is controlled by ADSL in our offices. It will be shown on examples that any movement of the snow cap provides a signal. The rate of repetition of these elementary signals is the indication of an increasing instability of the snow precursor to an avalanche. By comparing the acoustic signals to temperature variation evolution of the snow pack we could define an alarm degree allowing to secure the area.

The effect of vibratory disturbance on sexual behaviour of the southern green stink bug Nezara viridula (Heteroptera, Pentatomidae)

Abstract The effect of vibratory disturbance on sexual behaviour and substrate-borne sound communication of the southern green stink bug, Nezara viridula L. was studied. Disturbance signals do not change the time N. viridula males need to locate the source of vibratory signals, but decrease the number of males responding with the calling and courtship song to calling females. Female N. viridula proceed calling during stimulation with disturbance signals but some of them change the song rhythm by skipping one or more signal intervals or emitting the repelling signals. The number of females which change the dominant frequency of the calling song decreases proportionally with increasing differences between the dominant frequency of the disturbance signals and the emitted female calling song. Variation of the song dominant frequency probably serves females to avoid interference by increasing the signal to noise ratio. Signal duration and repetition rate do not change significantly when the female is stimulated with the disturbance signals. This indicates that frequency shift by calling females is the main strategy for reducing interference by competitive signalers in N. viridula vibrational communication.

Extraction of Harmonics Using Composite Observers

Online extraction of individual harmonics from repetitive signals using a composite asymptotic observer is presented in this paper. The settling period and the bandwidth of the observer depend on how far the observer poles have been placed from the origin of the s-plane or the z-plane. The errors in the magnitude and phase of the extracted components, due to the deviation of the signal from the central frequency of the observer, are made very small by providing an integrated phase-locking arrangement. Further improvement in the accuracy, particularly in the extracted higher harmonics, is due to the introduction of multirate sampling.

Analisis Ketepatan Penghitung Frekuensi dengan Metode Pencacahan Berbasis Mikrokontroler

A frequency counter is an electronic instrument, or component of one, that is used for measuring frequency. Frequency counters usually measure the number of oscillations or pulse per second in a repetitive electronic signal. A digital-signal frequency counter, can measure the number of positive-going-transition or the number of negative-going-transition of signal in a set of period time. This microcontroller-based frequency counter work by using a counter, which accumulates the number of negative-going-transitions occurring within two periods for 16-bit microcontroller-timer overflow. After the period, the value in the counter is divided by the period and transferred to a display. This frequency counter can measure frequency from 100 Hz to 1 MHz. The upper limit of frequency can be extended up to 256 MHz by adding a frequency divider. The analysis of the accuracy of measuring presented in this article can support to determine the number of digit to display.

Perfect Tracking of Repetitive Signals for a Class of Nonlinear Systems

Perfect tracking of the output of a class of nonlinear systems that has a unique response for a given input and is subject to repetitive reference input is considered in this paper. A conditional learning scheme guaranteeing sufficient knowledge can be learned iteratively to improve the input to achieve perfect tracking is proposed. The sufficient condition for monotonic convergence of the input sequence and the choice of the learning gains are given. The tracking performance of the proposed scheme is illustrated by a simulated example.

An On-Chip Multichannel Waveform Monitor for Diagnosis of Systems-on-a-Chip Integration

An on-chip multichannel waveform monitoring technique enhances built-in test and diagnostic capabilities of systems- on-a-chip (SoC) integration. The proposed multichannel monitor includes multiple probing front-end modules and a single shared waveform acquisition kernel that consists of an incremental variable step delay generator and an incremental reference voltage generator, featuring adaptive sample time generation for the operation of a target circuit and unidirectional waveform acquisition flow for area-efficient control. A 16-channel prototype in 0.18-mum CMOS technology demonstrated on-chip waveform acquisition at 40-ps and 200-muV resolutions. Combined on- and off-chip streamed-bit processing achieves background continuous waveform acquisition at 260 ms per single timing point for repetitive signals, while eliminating the integration of on-die high-capacity memory. A 700 mum times 600 mum area was occupied by a waveform acquisition kernel and an additional 60 mum times 100 mum area for each front-end module. The developed on-chip multichannel waveform monitoring technique is waveform accurate, area efficient, and suitable for diagnosis toward power supply and signal integrity in analog and digital circuits in mixed-signal SoC integration.

Spring cabbage peroxidases – Potential tool in biocatalysis and bioelectrocatalysis

Two fractions of peroxidase activity, cationic Px-cat and anionic Px-ani, were isolated and partially purified (143.5- and 5.49-fold, respectively) from homogenate of spring cabbage heads. Optimum pH for both fractions is 6.0; however, Px-cat is almost equally active at neutral pH (7.0) while Px-ani reveals high activity in more acidic pHs (with 60% of maximum activity at pH 3.0). Optimal temperature for both fractions was 40 °C. Px-ani possessed much higher thermal stability at 40–50 °C (60% of remaining activity after 144 h of incubation) than Px-cat. The peroxidases remained fully active during 4 weeks of storage at 4 °C. Kinetic studies revealed that Px-cat and Px-ani had lower apparent Km values for ABTS (0.0377 and 0.0625 mM) and o-dianisidine (0.357 and 0.286 mM) than for guaiacol (6.41 and 13.89 mM). The best substrate for Px-cat was pyrogallol and for Px-ani– o-dianisidine. Px-cat immobilized on polyanionic PyBA-modified carbon electrode was found to produce linear repetitive signals upon consecutive additions of hydrogen peroxide during at least 1-week period and to work effectively under buffered and non-buffered conditions. These properties were comparable with those of commercially available horseradish peroxidase. Stability of the hybrid bioelectrocatalytic film and low costs of extraction and partial purification of Px-cat make it a highly promising enzyme for practical applications, including construction of bioelectrodes.

Backside interferometric methods for localization of ESD-induced leakage current and metal shorts

Transient interferometric mapping (TIM) setup for ns-time ESD testing is adapted for post-stress failure analysis. Probing from the chip backside using the thermo-optical effect is used for localization of heating place related to failure. Two variants of 2D holographic interferometers, a Michelson and a “Wollaston” one, are used for a rough identification of a failure site. An adapted scanning heterodyne interferometer is used for accurate position determination with a 2 μm space resolution. The methods are applied to identify ESD damage and metal shorts. Sensitivity and space resolution are analyzed, supported by a 3D-thermal simulation of repetitive heating signal. A power sensitivity of 50 μW for a single point heat source is demonstrated.

Orangutans Modify Their Gestural Signaling According to Their Audience's Comprehension

When people are not fully understood, they persist with attempts to communicate, elaborating their speech in order to better convey their meaning [1]. We investigated whether captive orangutans (Pongo pygmaeus and Pongo abelii) would use analogous communicative strategies in signaling to a human experimenter, and whether they could distinguish different degrees of misunderstanding. Orangutans' behavior varied according to how well they had apparently been understood. When their aims were not met, they persisted in communicative attempts. However, when the interlocutor appeared partially to understand their meaning, orangutans narrowed down their range of signals, focusing on gestures already used and repeating them frequently. In contrast, when completely misunderstood, orangutans elaborated their range of gestures, avoiding repetition of failed signals. It is therefore possible, from communicative signals alone, to determine how well an orangutan's intended goal has been met. This differentiation might function under natural conditions to allow an orangutan's intended goals to be understood more efficiently. In the absence of conventional labels, communicating the fact that an intention has been somewhat misunderstood is an important way to establish shared meaning.

Accurate Spectral Analysis of Repetitive Signals Composed of Components Nonsynchronous With the Sampling Clock

A method for the accurate spectral analysis of signals containing components that do not require synchronism either with each other or with the sampling clock is presented. The method employs an algorithm based on the quadrature amplitude demodulation which is applied in a number of stages to achieve an accurate decomposition of a given time domain signal into frequency components. Using the simulated signal examples, the suitability of the method for the analysis of noisy quantized nonrepetitive signals is considered. When compared to the discrete Fourier transform, the benefits of using the method for the accurate detection of nonsynchronous tones in a signal are demonstrated

Singular spectrum analysis applied to ultrasonic detection and imaging of brachytherapy seeds

Ultrasound-guided brachytherapy using titanium-shelled radioactive seeds is a popular, effective means of treating prostate cancer. Unfortunately, implantation using needles inserted transperitoneally causes gland movement and distortion, which often results in seed misplacement and dosimetry errors. If actual seed locations could be determined in the operating room, then corrections to dosimetry errors could be made immediately. However, seed specularity, shadowing, and tissue clutter make imaging seeds difficult using conventional ultrasound. Singular spectrum analysis (SSA) shows promise for reliably imaging radioactive seeds implanted in the prostate and enabling additional corrective implantations to be made in the operating room. SSA utilizes eigenvalues derived from the diagonalized correlation matrix of envelope-detected radio-frequency echo signals to yield a P value indicative of the likelihood of a seed-specific repetitive signal. We demonstrated the potential of SSA for seed detection and imaging and illustrated the trade-off considerations for optimization of SSA in clinical applications using simulations assessing performance as a function of different levels of noise and the presence of repetitive signals with various repetition periods; experiments in an ideal scattering environment; and experiments using seeds implanted in beef.

Odontocete nasalizations: Morphology, physiology, and evolution of sonar signal generation in toothed whales

The odontocete nasal apparatus contains tissue complexes that generate a variety of sounds. Sounds are produced by moving air across the phonic lips, internal structures that were formed by the invagination of the ancient nasal openings. X-ray computed tomography shows this sound generation complex bilaterally in all odontocetes except in sperm whales, where it is unilateral. Two bottlenose dolphins provided simultaneous bilateral recordings of internal nasal cavity pressure and nasal tissue motion. Small catheters measured pneumatic pressure changes within each bony nasal passage; high-speed video endoscopy recorded motion at both pairs of phonic lips; and two hydrophones revealed acoustic pressure during target discrimination. Sonar pulses can be generated at the left and right phonic lips, independently or simultaneously. Air pressure in both bony nasal passages rises and falls together, even if the activity patterns at the two pairs of lips are different. Increasing pulse repetition rate or sound pressure levels are all normally accompanied by increasing nasal air pressure. The bilateral arrangement of sonar sources in the odontocete nose provides a basis for reinterpretation of previous findings; reevaluation of physiologic limits and on pulse repetition rate, signal bandwidth, frequency composition, and transmission beam geometry; and the evolution of this system.

Hidden Markov model-based packet loss concealment for voice over IP

As voice over IP proliferates, packet loss concealment (PLC) at the receiver has emerged as an important factor in determining voice quality of service. Through the use of heuristic variations of signal and parameter repetition and overlap-add interpolation to handle packet loss, conventional PLC systems largely ignore the dynamics of the statistical evolution of the speech signal, possibly leading to perceptually annoying artifacts. To address this problem, we propose the use of hidden Markov models for PLC. With a hidden Markov model (HMM) tracking the evolution of speech signal parameters, we demonstrate how PLC is performed within a statistical signal processing framework. Moreover, we show how the HMM is used to index a specially designed PLC module for the particular signal context, leading to signal-contingent PLC. Simulation examples, objective tests, and subjective listening tests are provided showing the ability of an HMM-based PLC built with a sinusoidal analysis/synthesis model to provide better loss concealment than a conventional PLC based on the same sinusoidal model for all types of speech signals, including onsets and signal transitions

SU‐FF‐J‐10: A Novel Signal‐Processing Strategy for in Vivo Ultrasonic Imaging of Brachytherapy Seeds

Purpose: Brachytherapy is proving to be a well‐accepted means of treating prostate cancer. Unfortunately, implantation using needles inserted transperineally causes gland movement, and the resulting distortion may cause seed misplacement and dosimetry errors. Our approach employs novel methods of digitally processing ultrasound echo signals to markedly improve ultrasonic imaging of seeds during the implantation procedure. This approach will enable the radiation oncologist to determine where all implanted seeds are located and to make additional implantations to correct for dosimetry errors cause by misplaced seeds.Method and Materials: Our signal‐processing strategy uses singular spectrum analysis (SSA) and shows promise for ultrasonically detecting and imaging radioactive seeds implanted in the prostate. This SSA‐based strategy utilizes pairs of eigenvalues derived from the autocorrelation matrix of envelope‐detected radiofrequency echo signals to identify seed‐specific signal repetitions. The power spectrum associated with a repetition signal is computed to derive a P‐value indicative of the likelihood of the presence of a seed at the location of that repetitive signal. P‐values throughout each scan plane are then color‐coded and superimposed on the corresponding conventional grayscale ultrasound images. These new ultrasound images are thus readily usable by clinicians to locate seeds. Results: Simulations assessing performance as a function of different levels of white and speckle noise and in the presence of signals at repetition periods not associated with seeds; experiments in an ideal scattering environment; and in vitro experiments using seeds implanted in beef were conducted and led to encouraging results. Simulations showed robustness to noise (signal‐to‐noise ratio < 25 dB) and in vitro experiments allowed for seed detection and imaging. Conclusion: Overall, our SSA‐based strategy shows encouraging potential for seed detection and imaging in the operating room. Clinical implementation of this methodology would be straightforward because it uses enveloped‐detected signals directly available from clinical scanners.

Improved maximum likelihood frequency offset estimation based on likelihood metric design

For emerging high data-rate communication systems in highly dispersive channels such as ultrawideband (UWB) systems, possible frequency offsets could be larger than the estimation range of the existing methods using training signals with identical parts or repetitive training signals (i.e., the training signals are composed of several identical subblocks or are obtained by repeating a training subblock for several times). This paper presents a novel improved maximum likelihood frequency offset estimator which can handle at least twice the estimation range of the existing methods using training signals with identical parts and achieves a better estimation performance. Based on the likelihood metric, a new design metric is introduced which is a pair-wise error probability (PEP) between the correct frequency offset point and a trial frequency offset point. The proposed PEP metric gives more theoretical insights on the performance of practical maximum likelihood estimators. How to design the PEP to achieve both a larger estimation range and a better estimation performance in fading channel environments is also presented and the corresponding estimator implementation is described.