Detection of frequency-modulated calls using a chirp model
Keywords:Acoustic noise, Algorithms, Approximation theory, Costs, Data compression, Frequency modulation, Linear equations, Mathematical models, Parameter estimation, Polynomials, Problem solving, Signal detection, Cetacean volcalizations, Chirp Models, Computational costs, Frequency-Modulated Calls
AbstractMany cetacean vocalisations are tonal and most are frequency-modulated. The detection algorithm presented here breaks the frequency contour into a sequence of elements. Each element is sufficiently short that a linear approximation to the frequency contour can be made. In this way the problem is simplified from that of detection of an unknown signal, to the detection of a known signal (a linear chirp) with unknown parameters. The method of estimation is based on maximum likelihood, and the start frequency, chirp rate and amplitude of each element are estimated. Further analysis is then carried out on groups of concatenated chirps (i.e. calls) to classify them. Results are given on performance for the supplied test recording and for synthetic signals in white noise. The pros of the algorithm are: good detection performance, at least in white noise; high resolution; ease of interpretation; flexibility; data compression. The cons are: computational cost; deterioration, of performance in non-white noise or with amplitude-modulated signals. Further development is needed to reduce errors with overlapping tonal or non-tonal signals. The algorithm is currently being applied to the problem of detecting right whale vocalisations and distinguishing them from those of humpback whales.
How to Cite
Copyright on articles is held by the author(s). The corresponding author has the right to grant on behalf of all authors and does grant on behalf of all authors, a worldwide exclusive licence (or non-exclusive license for government employees) to the Publishers and its licensees in perpetuity, in all forms, formats and media (whether known now or created in the future)
i) to publish, reproduce, distribute, display and store the Contribution;
ii) to translate the Contribution into other languages, create adaptations, reprints, include within collections and create summaries, extracts and/or, abstracts of the Contribution;
iii) to exploit all subsidiary rights in the Contribution,
iv) to provide the inclusion of electronic links from the Contribution to third party material where-ever it may be located;
v) to licence any third party to do any or all of the above.