Parametric modelling of cetacean calls
Parametric modelling of cetacean calls
This thesis is concerned with the detection and characterisation of tonal cetacean call through notch filter modelling. The recognition of these calls is based on their frequency evolution, and different approaches to estimating this are described. Adaptive notch filters (ANF) are viewed and compared through simulations. A novel RLS-based algorithm for estimating the local sweep rate of a frequency evolution is then developed. Biasing the frequency tracker’s update law towards this sweep rate permits one to resolve confusion problems at frequency crossings as well as during strong interfering sounds, such as cetacean clicks, that would otherwise disturb the tracking. A click pre-detection algorithm is developed and coupled to the frequency tracker. Further, a novel detection methodology based on the local reliability of the ANF parameter estimates is developed and analysed. The reliability is measured by the curvature of the cost function Hessian, and detections are made from periods of reliable estimation.
The thesis also investigates block-based approaches to frequency estimation. Time-varying AR (TVAR) models are improved and their properties in additive noise analysed. Block-based notch filters are developed and found to be more noise robust than TVAR models. However, estimation is more difficult than with ANF and the noise robustness is similar.
Comparing the most suitable of the parametric model approaches to a recently published spectrogram-based whistle processing algorithm, it is found that the ANF-based methods are more reliable and have better performance on recordings of tonals and isolated clicks. They are able to track rapidly sweeping tonals and cope well with frequency crossings. The detection methodology gives very few false alarms and permits accurate determination of start and end times of multiple simultaneous tonals.
University of Southampton
Johannson, Anders Torbjörn
ebca512a-a8df-45ae-88e3-43043dfe230c
2004
Johannson, Anders Torbjörn
ebca512a-a8df-45ae-88e3-43043dfe230c
Johannson, Anders Torbjörn
(2004)
Parametric modelling of cetacean calls.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
This thesis is concerned with the detection and characterisation of tonal cetacean call through notch filter modelling. The recognition of these calls is based on their frequency evolution, and different approaches to estimating this are described. Adaptive notch filters (ANF) are viewed and compared through simulations. A novel RLS-based algorithm for estimating the local sweep rate of a frequency evolution is then developed. Biasing the frequency tracker’s update law towards this sweep rate permits one to resolve confusion problems at frequency crossings as well as during strong interfering sounds, such as cetacean clicks, that would otherwise disturb the tracking. A click pre-detection algorithm is developed and coupled to the frequency tracker. Further, a novel detection methodology based on the local reliability of the ANF parameter estimates is developed and analysed. The reliability is measured by the curvature of the cost function Hessian, and detections are made from periods of reliable estimation.
The thesis also investigates block-based approaches to frequency estimation. Time-varying AR (TVAR) models are improved and their properties in additive noise analysed. Block-based notch filters are developed and found to be more noise robust than TVAR models. However, estimation is more difficult than with ANF and the noise robustness is similar.
Comparing the most suitable of the parametric model approaches to a recently published spectrogram-based whistle processing algorithm, it is found that the ANF-based methods are more reliable and have better performance on recordings of tonals and isolated clicks. They are able to track rapidly sweeping tonals and cope well with frequency crossings. The detection methodology gives very few false alarms and permits accurate determination of start and end times of multiple simultaneous tonals.
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Published date: 2004
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Local EPrints ID: 465356
URI: http://eprints.soton.ac.uk/id/eprint/465356
PURE UUID: 8164bed8-7866-42ee-a4a7-f5c7e76f5554
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Date deposited: 05 Jul 2022 00:39
Last modified: 16 Mar 2024 20:07
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Author:
Anders Torbjörn Johannson
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