Maciej Lopatka

Bio: Maciej Lopatka is an academic researcher from University of Paris. The author has contributed to research in topics: Sperm whale & Filter (signal processing). The author has an hindex of 6, co-authored 13 publications receiving 118 citations. Previous affiliations of Maciej Lopatka include Wrocław University of Technology.

Male sperm whale acoustic behavior observed from multipaths at a single hydrophone

Abstract: Sperm whales generate transient sounds (clicks) when foraging. These clicks have been described as echolocation sounds, a result of having measured the source level and the directionality of these signals and having extrapolated results from biosonar tests made on some small odontocetes. The authors propose a passive acoustic technique requiring only one hydrophone to investigate the acoustic behavior of free-ranging sperm whales. They estimate whale pitch angles from the multipath distribution of click energy. They emphasize the close bond between the sperm whale’s physical and acoustic activity, leading to the hypothesis that sperm whales might, like some small odontocetes, control click level and rhythm. An echolocation model estimating the range of the sperm whale’s targets from the interclick interval is computed and tested during different stages of the whale’s dive. Such a hypothesis on the echolocation process would indicate that sperm whales echolocate their prey layer when initiating their dives and follow a methodic technique when foraging.

Measuring the off-axis angle and the rotational movements of phonating sperm whales using a single hydrophone

Abstract: The common use of the bent-horn model of the sperm whale sound generator describes sperm whale clicks as the pulse series {p0,p1,p2,p3,…}. Clicks, however, deviate from this standard when recorded using off-axis hydrophones. The existence of additional pulses within the {p0,p1,p2,p3,…} series can be explained still using the bent-horn model. Multiple reflections on the whale’s frontal and distal sacs of the p0 pulse lead to additional sets of pulses detectable using a farfield, off-axis hydrophone. The travel times of some of these additional pulses depend on the whale’s orientation. The authors propose a method to estimate the off-axis angle of sperm whale clicks. They also propose a method to determine the nature of the movement (if it is pitch, yaw, or roll) of phonating sperm whales. The application of both methods requires the measurement of the travel time differences between pulses composing a sperm whale click. They lead, using a simple apparatus consisting of a single hydrophone at an unknown dep...

Non-Stationary Time-Series Segmentation Based on the Schur Prediction Error Analysis

Abstract: This paper proposes a non-stationary time-series segmentation method based on the analysis of the forward prediction error issued from the adaptive Schur orthogonal signal parameterisation. There is no a priori information about the analysed signal thus this method can be easily adapted to a large family of different types of signals for which two different stochastic processes are present. In this paper we set out some of the advantages of the adaptive Schur filter in deducing the presence of different non-stationary transient or long-term events leading to the signal segmentation. For each sample, the adaptive Schur algorithm calculates the optimal second-order solution for the signal prediction resulting in a set of time-varying model parameters (inter alia forward prediction error). We define the likelihood ratio (LR) test based on the Schur forward prediction error that is evaluated at each sample, thus giving excellent time-reaction properties. The LR test allows us to effectively partition the analysed time-series into homogeneous segments by considering its second-order statistics which are tracked adaptively by the Schur filter. The results performed by applying the proposed method to simulated signals are shown to verify its high performance

Passive Acoustic Monitoring of Cetaceans

Abstract: Acknowledgements Introduction Part I. Underwater Acoustics (The Basics): 1. Principles of underwater sound 2. Cetacean sounds 3. Sonar equation Part II. Signal Processing (Designing the Tools): 4. Detection methods 5. Classification methods 6. Localisation and tracking Part III. Passive Acoustic Monitoring (Putting It All Together): 7. Applications of PAM 8. Detection functions 9. Simulating sampling strategies 10. PAM systems 11. References and literature Index.

Recording and quantification of ultrasonic echolocation clicks from free-ranging toothed whales

Abstract: Toothed whales produce short, ultrasonic clicks of high directionality and source level to probe their environment acoustically. This process, termed echolocation, is to a large part governed by the properties of the emitted clicks. Therefore derivation of click source parameters from free-ranging animals is of increasing importance to understand both how toothed whales use echolocation in the wild and how they may be monitored acoustically. This paper addresses how source parameters can be derived from free-ranging toothed whales in the wild using calibrated multi-hydrophone arrays and digital recorders. We outline the properties required of hydrophones, amplifiers and analog to digital converters, and discuss the problems of recording echolocation clicks on the axis of a directional sound beam. For accurate localization the hydrophone array apertures must be adapted and scaled to the behavior of, and the range to, the clicking animal, and precise information on hydrophone locations is critical. We provide examples of localization routines and outline sources of error that lead to uncertainties in localizing clicking animals in time and space. Furthermore we explore approaches to time series analysis of discrete versions of toothed whale clicks that are meaningful in a biosonar context.