scholarly journals Caller ID for Risso's and Pacific White-Sided Dolphins

2021 ◽  
Author(s):  
Mahdi Al-Badrawi ◽  
Yue Liang ◽  
Kerri D. Seger ◽  
Christopher M. Foster ◽  
Nicholas J. Kirsch
Keyword(s):  
Ecosystem Dynamics ◽  
The Arctic ◽  
Noise Levels ◽  
Temperate Water ◽  
High Background ◽  
Temporal Properties ◽  
Mode Decomposition ◽  
High Background Noise ◽  
Audio Files ◽  
Water Species

Abstract Climate change affects the distributions of marine mammals1, and some temperate water species are spreading northward into the Arctic Ocean2, 3. Tracking expanding species is crucial to conservation efforts and using automatic detectors and classifiers to track the locations of their vocalizations could help. Risso’s (Gg) and Pacific white-sided (Lo) dolphins were documented spreading poleward2 and make very similar sounds, making it difficult for both human analysts and classification algorithms to tell them apart. Variational Mode Decomposition (VMD) has provided both an easier visualization tool4 for human analysts and offers promising capabilities in separating call types of similar spectral and temporal properties. Here we show a new visualization tool and feature extraction technique using VMD that achieves 81.3% accuracy, even when using audio files with faint signals and high background noise levels and without context clues. Because not all dolphins whistle5–7, being able to distinguish between just their pulsed signals is important for tracking them using as many files as possible from under-sampled areas of the ocean. Automating the VMD method and expanding it to other dolphin species that have very similar pulsive signals will lead to a faster understanding of ecosystem dynamics under a changing climate than can currently be achieved.

A Seismic Refraction Profile Across the Polar Continental Shelf of the Queen Elizabeth Islands

1971 ◽  
Vol 8 (3) ◽  
pp. 347-360 ◽  
Author(s):  
M. J. Berry ◽  
K. G. Barr
Keyword(s):  
Continental Slope ◽  
Broad Band ◽  
Seismic Refraction ◽  
Low Frequency ◽  
Water Layer ◽  
Noise Levels ◽  
High Background ◽  
Crustal Model ◽  
Seismic Recording ◽  
High Background Noise

During the spring of 1967, a seismic refraction experiment was conducted from the SW tip of Prince Patrick Island in the Queen Elizabeth Islands of Arctic Canada to a point mid-way down the continental slope, some 220 km from the coast.It was found that seismic recording on sea ice was plagued by unusually high background noise levels which could be attributed to low frequency (below 1 Hz) oscillations of the ice pans and to the broad-band noise generated by frequent ice cracking. It was discovered, and is shown theoretically, that seismic wave propagating through a water layer (the ocean) and incident on the ice layer from below provide an exact π/2 phase shift between the horizontal and vertical components of surface motion. This fact can be used to advantage in digital processing.The interpretation shows a crustal model with depths to the M discontinuity of 28 ± 4 km at the coast, thinning to 15 ± 9 km at the end of the profile. The velocity of the mantle is measured as 8.05 ± 0.17 km/s. Mid-way down the continental slope there are 5.0 ± 1.63 km of sediments overlying material with a velocity of 5.36 ± 0.15 km/s. Material of a similar velocity, 5.72 ± 0.18 km/s, lies 2.7 ± 1.9 km beneath the surface material at the coast, where the surface layer has a velocity of 4.76 ± 0.4 km/s. It is concluded that the data support the hypothesis that the Canada Basin has an oceanic rather than a continental crust.

Effects of Classroom Noise on Students and Teachers in Greece

2003 ◽  
Vol 96 (2) ◽  
pp. 539-544 ◽  
Author(s):  
Dimitris Skarlatos ◽  
Manolis Manatakis
Keyword(s):  
High School ◽  
Background Noise ◽  
Reverberation Time ◽  
Noise Levels ◽  
High Background ◽  
High Noise ◽  
Significant Percentage ◽  
Time Period ◽  
High Background Noise

Measurements inside 32 occupied high-school classrooms during the courses showed that the measured long-term equivalent noise levels are high. A significant percentage of students and teachers found these levels unacceptable. The observed noise levels depend on the time period of the course, the age, and the number of the students in each classroom. The large reverberation time and the high background noise are responsible for the measured high noise level.

scholarly journals Decision making in the face of a deadly predator: high-amplitude behavioural thresholds can be adaptive for rainforest crickets under high background noise levels

2020 ◽  
Vol 375 (1802) ◽  
pp. 20190471 ◽  
Author(s):  
Heiner Römer ◽  
Marc Holderied
Keyword(s):  
Background Noise ◽  
Experimental Tests ◽  
High Amplitude ◽  
Decision Criterion ◽  
Target Strength ◽  
False Alarms ◽  
Noise Levels ◽  
High Background ◽  
Ultrasonic Calls ◽  
High Background Noise

Many insect families have evolved ears that are adapted to detect ultrasonic calls of bats. The acoustic sensory cues indicating the presence of a bat are then used to initiate bat avoidance behaviours. Background noise, in particular at ultrasonic frequencies, complicates these decisions, since a response to the background may result in costly false alarms. Here, we quantify bat avoidance responses of small rainforest crickets (Gryllidae, Trigoniinae), which live under conditions of high levels of ultrasonic background noise. Their bat avoidance behaviour exhibits markedly higher thresholds than most other studied eared insects. Their responses do not qualitatively differ at suprathreshold amplitudes up to sound pressure levels of 105 dB. Moreover, they also exhibit evasive responses to single, high-frequency events and do not require the repetitive sequence of ultrasonic calls typical for the search phase of bat echolocation calls. Analysis of bat and katydid sound amplitudes and peak frequencies in the crickets' rainforest habitat revealed that the cricket's behavioural threshold would successfully reject the katydid background noise. Using measurements of the crickets' echo target strength for bat predators, we calculated the detection distances for both predators and prey. Despite their high behavioural threshold, the cricket prey still has a significant detection advantage at frequencies between 20 and 40 kHz. The low-amplitude bat calls they ignore are no predation threat because even much louder calls would be detected before the bat would hear the cricket echo. This leaves ample time for evasive actions. Thus, a simple decision criterion based on a high-amplitude behavioural threshold can be adaptive under the high background noise levels in nocturnal rainforests, in avoiding false alarms and only missing detection for bat calls too far away to pose a risk. This article is part of the theme issue ‘Signal detection theory in recognition systems: from evolving models to experimental tests’.

scholarly journals Separating overlapping echolocation: An updated method for estimating the number of echolocating animals in high background noise levels

2021 ◽  
Vol 150 (2) ◽  
pp. 709-717
Author(s):  
Rebecca A. Hamilton ◽  
Josefin Starkhammar ◽  
Stefanie K. Gazda ◽  
Richard C. Connor
Keyword(s):  
Background Noise ◽  
Noise Levels ◽  
High Background ◽  
High Background Noise

Improved Vancouver Raman Algorithm Based on Empirical Mode Decomposition for Denoising Biological Samples

2019 ◽  
Vol 73 (12) ◽  
pp. 1436-1450 ◽  
Author(s):  
Fabiola León-Bejarano ◽  
Martin O. Méndez ◽  
Miguel G. Ramírez-Elías ◽  
Alfonso Alba
Keyword(s):  
Empirical Mode Decomposition ◽  
Raman Spectra ◽  
Biological Samples ◽  
Biological Material ◽  
Noise Levels ◽  
Synthetic Material ◽  
High Noise ◽  
Mode Decomposition ◽  
Mean Filter ◽  
The Mean

A novel method based on the Vancouver Raman algorithm (VRA) and empirical mode decomposition (EMD) for denoising Raman spectra of biological samples is presented. The VRA is one of the most used methods for denoising Raman spectroscopy and is composed of two main steps: signal filtering and polynomial fitting. However, the signal filtering step consists in a simple mean filter that could eliminate spectrum peaks with small intensities or merge relatively close spectrum peaks into one single peak. Thus, the result is often sensitive to the order of the mean filter, so the user must choose it carefully to obtain the expected result; this introduces subjectivity in the process. To overcome these disadvantages, we propose a new algorithm, namely the modified-VRA (mVRA) with the following improvements: (1) to replace the mean filter step by EMD as an adaptive parameter-free signal processing method; and (2) to automate the selection of polynomial degree. The denoising capabilities of VRA, EMD, and mVRA were compared in Raman spectra of artificial data based on Teflon material, synthetic material obtained from vitamin E and paracetamol, and biological material of human nails and mouse brain. The correlation coefficient (ρ) was used to compare the performance of the methods. For the artificial Raman spectra, the denoised signal obtained by mVRA ([Formula: see text]) outperforms VRA ([Formula: see text]) for moderate to high noise levels whereas mVRA outperformed EMD ([Formula: see text]) for high noise levels. On the other hand, when it comes to modeling the underlying fluorescence signal of the samples (i.e., the baseline trend), the proposed method mVRA showed consistent results ([Formula: see text]. For Raman spectra of synthetic material, good performance of the three methods ([Formula: see text] for VRA, [Formula: see text] for EMD, and [Formula: see text] for mVRA) was obtained. Finally, in the biological material, mVRA and VRA showed similar results ([Formula: see text] for VRA, [Formula: see text] for EMD, and [Formula: see text] for mVRA); however, mVRA retains valuable information corresponding to relevant Raman peaks with small amplitude. Thus, the application of EMD as a filter in the VRA method provides a good alternative for denoising biological Raman spectra, since the information of the Raman peaks is conserved and parameter tuning is not required. Simultaneously, EMD allows the baseline correction to be automated.

scholarly journals Exponentially decaying modes and long-term prediction of sea ice concentration using Koopman mode decomposition

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
James Hogg ◽  
Maria Fonoberova ◽  
Igor Mezić
Keyword(s):  
Sea Ice ◽  
Annual Variation ◽  
Temporal Dynamics ◽  
The Arctic ◽  
Sea Ice Concentration ◽  
Mode Decomposition ◽  
Spatial Modes ◽  
Ice Concentration ◽  
The Mean ◽  
Insight Into

Abstract Sea ice cover in the Arctic and Antarctic is an important indicator of changes in the climate, with important environmental, economic and security consequences. The complexity of the spatio-temporal dynamics of sea ice makes it difficult to assess the temporal nature of the changes—e.g. linear or exponential—and their precise geographical loci. In this study, Koopman Mode Decomposition (KMD) is applied to satellite data of sea ice concentration for the Northern and Southern hemispheres to gain insight into the temporal and spatial dynamics of the sea ice behavior and to predict future sea ice behavior. We observe spatial modes corresponding to the mean and annual variation of Arctic and Antarctic sea ice concentration and observe decreases in the mean sea ice concentration from early to later periods, as well as corresponding shifts in the locations that undergo significant annual variation in sea ice concentration. We discover exponentially decaying spatial modes in both hemispheres and discuss their precise spatial extent, and also perform predictions of future sea ice concentration. The Koopman operator-based, data-driven decomposition technique gives insight into spatial and temporal dynamics of sea ice concentration not apparent in traditional approaches.

A Novel Approach for Detection of Bearing Defects from Noisy Vibration Signal

2014 ◽  
Vol 592-594 ◽  
pp. 2001-2005
Author(s):  
Deepak Paliwal ◽  
Achintya Choudhury ◽  
T. Govardhan ◽  
Saurabh Singh Chandrawat
Keyword(s):  
Signal To Noise Ratio ◽  
Vibration Signal ◽  
High Background ◽  
Related Information ◽  
Bearing Defects ◽  
Novel Approach ◽  
Deep Groove ◽  
Deep Groove Ball Bearing ◽  
High Background Noise ◽  
Inner Race

Vibration signal of a defective bearing carries fault related information. The aim of this paper is to develop a signal processing methodology that identifies the presence of defect from bearing vibration signal subjected high background noise. A simulated vibration signal considering inner race defect in a deep groove ball bearing with low signal to noise ratio has been generated and investigated. A technique involving CWT of vibration signal and post-processing though FFT has been adopted to analyze the signal. Results show that proposed methodology can yield the presence of inner race defect prominently from a noisy vibration signal.

scholarly journals Variability scaling and consistency in airborne and satellite altimetry measurements of Arctic sea ice

2020 ◽  
Vol 14 (2) ◽  
pp. 751-767
Author(s):  
Shiming Xu ◽  
Lu Zhou ◽  
Bin Wang
Keyword(s):  
Remote Sensing ◽  
Sea Ice ◽  
Snow Depth ◽  
Spatial Scales ◽  
Ice Cover ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
First Year ◽  
Noise Levels ◽  
Wide Range

Abstract. Satellite and airborne remote sensing provide complementary capabilities for the observation of the sea ice cover. However, due to the differences in footprint sizes and noise levels of the measurement techniques, as well as sea ice's variability across scales, it is challenging to carry out inter-comparison or consistently study these observations. In this study we focus on the remote sensing of sea ice thickness parameters and carry out the following: (1) the analysis of variability and its statistical scaling for typical parameters and (2) the consistency study between airborne and satellite measurements. By using collocating data between Operation IceBridge and CryoSat-2 (CS-2) in the Arctic, we show that consistency exists between the variability in radar freeboard estimations, although CryoSat-2 has higher noise levels. Specifically, we notice that the noise levels vary among different CryoSat-2 products, and for the European Space Agency (ESA) CryoSat-2 freeboard product the noise levels are at about 14 and 20 cm for first-year ice (FYI) and multi-year ice (MYI), respectively. On the other hand, for Operation IceBridge and NASA's Ice, Cloud, and land Elevation Satellite (ICESat), it is shown that the variability in snow (or total) freeboard is quantitatively comparable despite more than a 5-year time difference between the two datasets. Furthermore, by using Operation IceBridge data, we also find widespread negative covariance between ice freeboard and snow depth, which only manifests on small spatial scales (40 m for first-year ice and about 80 to 120 m for multi-year ice). This statistical relationship highlights that the snow cover reduces the overall topography of the ice cover. Besides this, there is prevalent positive covariability between snow depth and snow freeboard across a wide range of spatial scales. The variability and consistency analysis calls for more process-oriented observations and modeling activities to elucidate key processes governing snow–ice interaction and sea ice variability on various spatial scales. The statistical results can also be utilized in improving both radar and laser altimetry as well as the validation of sea ice and snow prognostic models.

Transition detection for laminar flow aircraft using microphones beneath the surface of laser drilled suction panels

2000 ◽  
Vol 214 (3) ◽  
pp. 143-155
Author(s):  
R V Barrett
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Laminar Flow ◽  
Reynolds Numbers ◽  
Suction Surface ◽  
Microphone Signal ◽  
High Background ◽  
Low Reynolds Numbers ◽  
High Background Noise ◽  
Suction Flow

The possibility of detecting transition through the very small laser drilled perforations in panels representing the suction surface of a hybrid laminar flow aircraft is examined. The method uses miniature microphones to detect changes to the noise received from the boundary layer. Tests using a flat plate rig in a low-turbulence wind tunnel at Reynolds numbers up to 3.8 million per metre, demonstrate that the boundary layer state can be defined in this manner, most simply through measurement of the root mean square (r.m.s.) of the microphone signal. It is shown that the r.m.s. reaches a peak in the transition zone and that when the boundary layer is fully turbulent the value is still significantly higher than it was before transition. Porosity in the range 0.8-6.4 percent was examined, with nominal hole diameters of 0.06 and 0.10 mm in 0.9 mm thick laser drilled suction surface specimens. Suction flow through the surface was found not adversely to affect the operation of the system. The experiment was limited to low Reynolds numbers because the high background noise in the wind tunnel made detection of the boundary layer element of the signal increasingly difficult to define as speed increased. It is considered that test in flight will be needed to prove fully the validity of the method. A preliminary design of an installation for this purpose is suggested that allows the suction flow to be maintained over the measuring region.

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