Clutter Level Research Articles

Sound source localization and segregation with internally coupled ears: the treefrog model.

Acoustic signaling plays key roles in mediating many of the reproductive and social behaviors of anurans (frogs and toads). Moreover, acoustic signaling often occurs at night, in structurally complex habitats, such as densely vegetated ponds, and in dense breeding choruses characterized by high levels of background noise and acoustic clutter. Fundamental to anuran behavior is the ability of the auditory system to determine accurately the location from where sounds originate in space (sound source localization) and to assign specific sounds in the complex acoustic milieu of a chorus to their correct sources (sound source segregation). Here, we review anatomical, biophysical, neurophysiological, and behavioral studies aimed at identifying how the internally coupled ears of frogs contribute to sound source localization and segregation. Our review focuses on treefrogs in the genus Hyla, as they are the most thoroughly studied frogs in terms of sound source localization and segregation. They also represent promising model systems for future work aimed at understanding better how internally coupled ears contribute to sound source localization and segregation. We conclude our review by enumerating directions for future research on these animals that will require the collaborative efforts of biologists, physicists, and roboticists.

A Neural-Network-Based Beamformer for Phased Array Weather Radar

Phased array weather radars, particularly with high temporal resolution, essentially need a robust and fast beamformer to accurately estimate precipitation profiles such as reflectivity and Doppler velocity. In this paper, we introduce a neural-network-based beamformer to address this problem. In particular, the optimum weight vector is computed by modeling the problem as a three-layer radial basis function neural network (RBFNN), which is trained with I/O pairs obtained from the optimum Wiener solution. The RBFNN was chosen because of its characteristic of accurate approximation and good generalization, and its robustness against interference and noise. The proposed RBFNN beamforming method is compared with traditional beamforming methods, namely, Fourier beamforming (FR), Capon beamforming, and the flower pollination algorithm (FPA), which is a recently proposed nature-inspired optimization algorithm. It is shown that the RBFNN approach has nearly optimal performance in various precipitation radar signal simulations relative to the rival methods. The validity of the RBFNN beamformer is demonstrated by using real weather data collected by the phased array radar (PAR) at Osaka University, and compared with, in addition to the FR and FPA methods, the minimum mean square error beamforming method. It is shown that the RBFNN method estimates the reflectivity of the PAR at Osaka University with less clutter level than those of the other three methods.

Experimental feasibility of multistatic holography for breast microwave radar image reconstruction.

The goal of this study was to assess the experimental feasibility of circular multistatic holography, a novel breast microwave radar reconstruction approach, using experimental datasets recorded using a preclinical experimental setup. The performance of this approach was quantitatively evaluated by calculating the signal to clutter ratio (SCR), contrast to clutter ratio (CCR), tumor to fibroglandular response ratio (TFRR), spatial accuracy, and reconstruction time. Five datasets were recorded using synthetic phantoms with the dielectric properties of breast tissue in the 1-6 GHz range using a custom radar system developed by the authors. The datasets contained synthetic structures that mimic the dielectric properties of fibroglandular breast tissues. Four of these datasets the authors covered an 8 mm inclusion that emulated a tumor. A custom microwave radar system developed at the University of Manitoba was used to record the radar responses from the phantoms. The datasets were reconstructed using the proposed multistatic approach as well as with a monostatic holography approach that has been previously shown to yield the images with the highest contrast and focal quality. For all reconstructions, the location of the synthetic tumors in the experimental setup was consistent with the position in the both the monostatic and multistatic reconstructed images. The average spatial error was less than 4 mm, which is half the spatial resolution of the data acquisition system. The average SCR, CCR, and TFRR of the images reconstructed with the multistatic approach were 15.0, 9.4, and 10.0 dB, respectively. In comparison, monostatic images obtained using the datasets from the same experimental setups yielded average SCR, CCR, and TFRR values of 12.8, 4.9, and 5.9 dB. No artifacts, defined as responses generated by the reconstruction method of at least half the energy of the tumor signatures, were noted in the multistatic reconstructions. The average execution time of the images formed using the proposed approach was 4 s, which is one order of magnitude faster than the current state-of-the-art time-domain multistatic breast microwave radar reconstruction algorithms. The images generated by the proposed method show that multistatic holography is capable of forming spatially accurate images in real-time with signal to clutter levels and contrast values higher than other published monostatic and multistatic cylindrical radar reconstruction approaches. In comparison to the monostatic holographic approach, the images generated by the proposed multistatic approach had SCR values that were at least 50% higher. The multistatic images had CCR and TFRR values at least 200% greater than those formed using a monostatic approach.

STATISTICAL ANALYSIS FOR TERENGGANU FORWARD SCATTER RADAR SEASIDE CLUTTER

The statistical analysis for Terengganu, Malaysia seaside clutter is presented in this paper. The measured clutter data were collected using a prototype of forward scatter radar (FSR) micro-sensor network with very high frequency (VHF) and ultra-high frequency (UHF) bands. Four categories of clutter strength were recorded during the measurements, which are low, medium, strong and very strong clutter. The classes were divided according to the wind speed occurred during the measurements period. The analysis is to determine the best-fit distribution model for the measured clutter data. Four types of distribution models are used in this analysis, which are Weibull, Gamma, Log-Logistic and Log-Normal distribution. One of the goodness of fit (GOF) tests called root mean square error (RMSE) is used to prove which distribution is a better fit to the probability distribution of the measured clutter data. The obtained results show that for 64 MHz with all clutter level strength, Weibull distribution provides better fit and records the lowest RMSE. Weibull distribution also fits best to the clutter data for low clutter of 151 MHz. However, for the rest of clutter level strength for 151 MHz, Gamma distribution is the best-fitted model with lowest RMSE values. Log-Logistic distribution proves to be the best fitted model to all clutter level strength of clutter data for 434 MHz with smallest RMSE values.

Variational Bayesian Expectation Maximization for Radar Map Estimation

For self-localization, a detailed and reliable map of the environment can be used to relate sensor data to static features with known locations. This paper presents a method for construction of detailed radar maps that describe the expected intensity of detections. Specifically, the measurements are modelled by an inhomogeneous Poisson process with a spatial intensity function given by the sum of a constant clutter level and an unnormalized Gaussian mixture. A substantial difficulty with radar mapping is the presence of data association uncertainties, i.e., the unknown associations between measurements and landmarks. In this paper, the association variables are introduced as hidden variables in a variational Bayesian expectation maximization (VBEM) framework, resulting in a computationally efficient mapping algorithm that enables a joint estimation of the number of landmarks and their parameters.

Ultrafast Harmonic Coherent Compound (UHCC) Imaging for High Frame Rate Echocardiography and Shear-Wave Elastography.

Transthoracic shear-wave elastography (SWE) of the myocardium remains very challenging due to the poor quality of transthoracic ultrafast imaging and the presence of clutter noise, jitter, phase aberration, and ultrasound reverberation. Several approaches, such as diverging-wave coherent compounding or focused harmonic imaging, have been proposed to improve the imaging quality. In this study, we introduce ultrafast harmonic coherent compounding (UHCC), in which pulse-inverted diverging waves are emitted and coherently compounded, and show that such an approach can be used to enhance both SWE and high frame rate (FR) B-mode Imaging. UHCC SWE was first tested in phantoms containing an aberrating layer and was compared against pulse-inversion harmonic imaging and against ultrafast coherent compounding (UCC) imaging at the fundamental frequency. In vivo feasibility of the technique was then evaluated in six healthy volunteers by measuring myocardial stiffness during diastole in transthoracic imaging. We also demonstrated that improvements in imaging quality could be achieved using UHCC B-mode imaging in healthy volunteers. The quality of transthoracic images of the heart was found to be improved with the number of pulse-inverted diverging waves with a reduction of the imaging mean clutter level up to 13.8 dB when compared against UCC at the fundamental frequency. These results demonstrated that UHCC B-mode imaging is promising for imaging deep tissues exposed to aberration sources with a high FR.

Hoarding among outpatients seeking treatment at a psychiatric hospital in Singapore

Hoarding symptoms commonly co-occur with other psychiatric disorders, such as major depressive disorder, and have been observed across cultures. Yet, few studies have examined hoarding in other disorders or in an Asian context. The present study aimed to determine: (1) the prevalence of clinically significant hoarding, (2) differences between participants with and without significant hoarding, and (3) predictors of hoarding severity in a Singaporean clinical sample. Five hundred outpatients with anxiety disorders, depressive disorders, schizophrenia, and pathological gambling completed a battery of questionnaires on hoarding, anxiety, depression, functional impairment due to clutter, and quality of life. Thirty percent of our sample reported significant hoarding. However, clutter levels in the hoarding group were low, and hoarding severity was not significantly linked to quality of life, after adjusting for anxiety and depression. In addition, depression – but not anxiety – predicted hoarding severity. Our results provide a cross-cultural perspective on hoarding symptoms, and replicate findings that support a link between depression and hoarding. The differential presentation of hoarding in our sample could be due to true cultural differences in hoarding pathology or to variant psychometric properties of the measures used. Further research evaluating hoarding in Asian contexts with different methodology is needed.

Amazon river dolphins (Inia geoffrensis) use a high-frequency short-range biosonar.

Toothed whales produce echolocation clicks with source parameters related to body size; however, it may be equally important to consider the influence of habitat, as suggested by studies on echolocating bats. A few toothed whale species have fully adapted to river systems, where sonar operation is likely to result in higher clutter and reverberation levels than those experienced by most toothed whales at sea because of the shallow water and dense vegetation. To test the hypothesis that habitat shapes the evolution of toothed whale biosonar parameters by promoting simpler auditory scenes to interpret in acoustically complex habitats, echolocation clicks of wild Amazon river dolphins were recorded using a vertical seven-hydrophone array. We identified 404 on-axis biosonar clicks having a mean SLpp of 190.3 ± 6.1 dB re. 1 µPa, mean SLEFD of 132.1 ± 6.0 dB re. 1 µPa(2)s, mean Fc of 101.2 ± 10.5 kHz, mean BWRMS of 29.3 ± 4.3 kHz and mean ICI of 35.1 ± 17.9 ms. Piston fit modelling resulted in an estimated half-power beamwidth of 10.2 deg (95% CI: 9.6-10.5 deg) and directivity index of 25.2 dB (95% CI: 24.9-25.7 dB). These results support the hypothesis that river-dwelling toothed whales operate their biosonars at lower amplitude and higher sampling rates than similar-sized marine species without sacrificing high directivity, in order to provide high update rates in acoustically complex habitats and simplify auditory scenes through reduced clutter and reverberation levels. We conclude that habitat, along with body size, is an important evolutionary driver of source parameters in toothed whale biosonars.

A review of automated image understanding within 3D baggage computed tomography security screening.

Baggage inspection is the principal safeguard against the transportation of prohibited and potentially dangerous materials at airport security checkpoints. Although traditionally performed by 2D X-ray based scanning, increasingly stringent security regulations have led to a growing demand for more advanced imaging technologies. The role of X-ray Computed Tomography is thus rapidly expanding beyond the traditional materials-based detection of explosives. The development of computer vision and image processing techniques for the automated understanding of 3D baggage-CT imagery is however, complicated by poor image resolutions, image clutter and high levels of noise and artefacts. We discuss the recent and most pertinent advancements and identify topics for future research within the challenging domain of automated image understanding for baggage security screening CT.

Targets Need Their Own Personal Space: Effects of Clutter on Multiple-Target Search Accuracy.

Visual search is an essential task for many lifesaving professions; airport security personnel search baggage X-ray images for dangerous items and radiologists examine radiographs for tumors. Accuracy is critical for such searches; however, there are potentially negative influences that can affect performance; for example, the displays can be cluttered and can contain multiple targets. Previous research has demonstrated that clutter can hurt search performance and a second target is less likely to be detected in a multiple-target search after a first target has been found, which raises a concern-how does clutter affect multiple-target search performance? The current study explored clutter in a multiple-target search paradigm, where there could be one or two targets present, and targets appeared in varying levels of clutter. There was a significant interaction between clutter and target number: Increasing levels of clutter did not affect single-target detection but did reduce detection of a second target. Multiple-target search accuracy is known to be sensitive to contextual influences, and the current results reveal a specific effect wherein clutter disproportionally affected multiple-target search accuracy. These results suggest that the detection and processing of a first target might enhance the masking effects of clutter around a second target.

Improving Route Directions: The Role of Intersection Type and Visual Clutter for Spatial Reference

SummaryIn this study, we ask whether references to paths and landmarks in route directions (RDs) are influenced by environmental complexity, zooming in on two aspects of the visual surroundings, namely intersection structure and visual clutter. Speakers are asked to produce (Experiment 1), understand (Experiment 2) and evaluate (Experiment 3) turn‐by‐turn RDs in a naturalistic setting (Google Street View panoramic pictures). We find that increased levels of visual clutter and intersections with complex structures trigger more references to landmarks and paths when participants produce RDs, longer decision times to determine what the next correct step in a route is and increased preference for landmarks. Finally, we discuss possible implications for automatic RD generation.Copyright © 2015 John Wiley & Sons, Ltd.

Time-Domain Wideband Adaptive Beamforming for Radar Breast Imaging

A novel wideband microwave radar imaging method is presented to detect regions of significant dielectric contrast within the breast. Clutter reduction is paramount to any radar imaging algorithm, especially with clinical patient data where the tissue composition of the breast is inhomogeneous. Time-domain data-adaptive imaging methods have been previously applied in a narrowband manner for microwave radar breast imaging when the received signal spectral content was wideband. In this study, a wideband time-domain adaptive imaging approach is presented to perform data-adaptive focusing across the spectrum to reduce clutter. An equalization filter is adapted to compensate for the propagation distortion through tissue using a calculated estimate of the average dielectric properties of the breast. The effectiveness of the proposed wideband adaptive imaging approach is evaluated in conjunction with the delay-and-sum (DAS) method using numerical, experimental, and clinical data. Target scatterers are clearly detected while clutter levels are reduced significantly, between 4 and 6 dB, when compared to the DAS technique.

Validation of the Clutter Image Rating in older adults with hoarding disorder.

The Clutter Image Rating (CIR) was created to meet a gap in the research on compulsive hoarding: how to ascertain clutter level in an individual's home without a home visit, as not all clinicians have the ability to conduct a home visit. The CIR has proven itself to be both reliable and valid for use in adults with compulsive hoarding symptoms. However, there is currently a dearth of information on performance of the CIR in older adults diagnosed with hoarding disorder (HD). Because older adults have increased medical issues, including fall risks, evaluating the level of clutter in the house is especially critical in geriatric populations. The current study was an investigation of the reliability and validity of the CIR in assessing late life HD. The internal consistency, convergent and divergent validity, and norms of the CIR were investigated in a large geriatric HD sample and compared with a midlife sample of individuals with HD. Criterion validity of the CIR was investigated through the comparison of participant ratings conducted in the clinic and clinician ratings conducted in the home. The current study found similar levels of reliability and validity in a late life sample as in previous studies conducted in mid-life adults. Unlike previous studies, the current study did not find a significant relationship between the CIR and the non-clutter related subscales of the Savings Inventory-Revised. The CIR appears to be both reliable and valid for assessing clutter levels in older adults diagnosed with HD.

In vivo application of short-lag spatial coherence and harmonic spatial coherence imaging in fetal ultrasound.

Fetal scanning is one of the most common applications of ultrasound imaging and serves as a source of vital information about maternal and fetal health. Visualization of clinically relevant structures, however, can be severely compromised in difficult-to-image patients due to poor resolution and the presence of high levels of acoustical noise or clutter. We have developed novel coherence-based beamforming methods called Short-Lag Spatial Coherence (SLSC) imaging and Harmonic Spatial Coherence imaging (HSCI), and applied them to suppress the effects of clutter in fetal imaging. This method is used to create images of the spatial coherence of the backscattered ultrasound as opposed to images of echo magnitude. We present the results of a patient study to assess the benefits of coherence-based beamforming in the context of first trimester fetal exams. Matched fundamental B-mode, SLSC, harmonic B-mode, and HSCI images were generated using raw radio frequency data collected on 11 volunteers in the first trimester of pregnancy. The images were compared for qualitative differences in image texture and target conspicuity as well as using quantitative imaging metrics such as signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and contrast. SLSC and HSCI showed statistically significant improvements across all imaging metrics compared with B-mode and harmonic B-mode, respectively. These improvements were greatest for poor quality B-mode images where contrast of anechoic targets was improved from 15 dB in fundamental B-mode to 27 dB in SLSC and 17 dB in harmonic B-mode to 30 dB in HSCI. CNR improved from 1.4 to 2.5 in the fundamental images and 1.4 to 3.1 in the harmonic case. These results exhibit the potential of coherence-based beamforming to improve image quality and target detectability, especially in high noise environments.

Communicating in a cacophony: Possible solutions to the cocktail party problem in treefrog choruses

Male treefrogs advertise for mates in dense assemblages characterized by high levels of noise and acoustic clutter. Non-mutually exclusive approaches to ameliorating the “cocktail party” problem in frog choruses could involve signal production or perception. Male neotropical Dendropsophus microcephalus employ multi-note calls and can rapidly alter inter-note timing to reduce call overlap. Adjustments are made selectively such that interference is most effectively reduced among closest neighbors. There is evidence that intensity and perhaps spatial cues contribute to this selectivity. Male gray treefrogs, Hyla versicolor, do not seem to exhibit selective attention in a way that reduces call interference among nearest neighbors, and changes made in call duration and rate that occur with increasing noise levels do not aid in signal detection by females. Moreover, auditory induction, by which the auditory system might perceptually restore masked or missing elements of pulsatile calls, does not seem to occur. Although, under some circumstances, differences in call frequency may help females distinguish among neighboring males, naturalistic spectral differences do not seem to help females perceptually separate the overlapping calls of such males. There is evidence, however, that spatial separation of males can contribute to signal segregation by listening females during acoustic interference.

Effects of perceptual complexity on older and younger adults’ target acquisition performance

The present study evaluated the effects of the three perceptual complexity factors: number of elements, colour variety, and graphical background clutter level, on older and younger adults’ target acquisition time within a computer display. Experiment 1 manipulated the total number of icons, Experiment 2 manipulated the variety of icon colours, and Experiment 3 manipulated the clutter level of the graphical background on the display. In each experiment, 12 older and 12 younger adults were asked to move a cursor to a target icon on the display as quickly and accurately as possible. Target size and distance to the cursor were also manipulated to yield different difficulties of targets. Target acquisition time and Fitts’ law slope were analysed. Results showed that target acquisition time increased for more difficult targets under all the three complexity factors. The amount of increase was more evident for the factors of colour variety and graphical background clutter than for the number of icons. Older participants performed more slowly than younger participants did, particularly for more difficult targets. However, the impact of the three complexity factors on acquisition time appeared to be comparable for both age groups. The results suggest that implementations of colour varieties and graphical backgrounds on interfaces should be restricted, especially when icon acquisition is a common activity involved in interacting with an interface.

Beamforming of sound from two-dimensional arrays using spatial matched filters.

Fully-sampled two-dimensional (2D) arrays can have two-way focusing of the ultrasound beam in both lateral directions leading to high quality, real-time three-dimensional (3D) imaging. However, fully-sampled 2D arrays with very large element counts (>16,000) are difficult to manufacture due to interconnect density and large element electrical impedance. As an alternative, row-column or crossed electrode arrays have been proposed to simplify transducer fabrication and system integration. These types of arrays consist of two one-dimensional arrays oriented perpendicular to each other. Using conventional delay-and-sum beamforming, each array performs one-way focusing in perpendicular lateral directions which yield higher sidelobe and acoustic clutter levels compared to fully-sampled 2D arrays with two-way focusing. In this paper, the use of spatial matched filters to improve focusing of row-column arrays is investigated. On receive, data from each element are first spatial match filtered in the elevation direction. After summation, the data are filtered again in the azimuth direction. Beam widths comparable to one-way focusing are seen in azimuth and beam widths comparable to two-way focusing are achieved in elevation. 3D beam patterns from computer simulation results using a 7.5 MHz 128 × 128 row-column array are shown with comparison to a fully sampled 2D array.

A Study on the Effects of Advertising Versus Publicity According to the Clutter Level

A Study on the Effects of Advertising Versus Publicity According to the Clutter Level

Time-to-arrival discrimination of multiple sound sources

Previous research in auditory detection of time-to-arrival (TTA) has tended to focus on single sound sources approaching a listener. However, visual studies of TTA have suggested that there may be different perceptual strategies employed with respect to single versus multiple objects on approach. The current research is designed to directly address the capacity and informational support of listeners to make determinations on the TTA of multiple sound sources. Initial experimentation evaluated the capacity for discrimination between a stationary and moving sound source. Additional studies evaluated multiple moving sound sources, with direct manipulation of their spectra to determine how various acoustic qualities contribute to TTA determinations. Results suggest the relative influence of intensity, frequency, and sound source dynamics as they facilitate competitive discriminations between approaching sound sources. Additional conclusions demonstrate changes in the use of spectral cues for lower and higher levels of auditory clutter as they might impact TTA.

Performance Analysis of Ground Moving Target Detection for Airborne MIMO Radar

The performance of a Ground Moving Target Indication (GMTI) radar is determined by the interference level of the clutter to a large extent. With the longer illumination and the larger aperture, Multiple-Input, Multiple-Output (MIMO) radar greatly enhances the ability to detect the slow-moving target. This paper compares MIMO radar with conventional phased-array radar in terms of signal to clutter and noise ratio (SCNR) performance. Moreover, the paper proves the fact that the improvement of SCNR with MIMO techniques is not only limited in the antenna configuration of the side-looking but also non-sidelooking array-antenna. The analysis of mianlobe clutter and sidelobe clutter levels can greatly simplify the computation of the total clutter. Finally, the experimental simulation is been given.