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Unsupervised Classification of Marine Soundscapewith Non-Negative Matrix Factorization
Yuen-Wa HO, Tzu-Hao LIN, Tomonari AKAMATSU, Leszek KARCZMARSKIEmail: [email protected]; Website: https://www.hku-cetacean-ecology.net/
METHODS
INTRODUCTION• Marine soundscape represents a combination of geophony, biophony and anthrophony in the marine
environment (i.e. sound of geological processes, biological sounds and anthropogenic noise)• Study species: Indo-Pacific humpback dolphin (Sousa chinensis)o Inhabits inshore coastal waters with depth < 20mo Highly susceptible to anthropogenic impacts
• This study aims to classify marine soundscape with nonnegative matrix factorization (NMF) with unsupervised approach to provide a quantitative acoustic measure of humpback dolphin habitats in Hong Kong waters
RESULTS• No prior labelling of the core habitat / non-core habitat is given in NMF decomposition (Unsupervised approach on spectral decomposition) • New encoding matrix of the entire input data (600 recordings) was trained by using NMF (Fig 2)• Decomposed spectral features were used to classify site-specific soundscape composition (Fig 3) (Supervised classification of marine soundscape)• Spatial change of relative strength of each basis in different recording locations were constructed (Fig 4)
DISCUSSION• Coastal soundscape vary spatially in the habitat of Indo-Pacific humpback dolphins in Hong Kong waters• Relative Strength of Spectral Characteristics corresponds with dolphin distribution data• Information retrieval of sound-source contribution improves traditional approach delineating strength of
spectral contribution along different frequency ranges
Power Spectral Density (PSD) measurement by Discrete Fourier
Transform (DFT) at 250 Hz interval between 250 Hz – 48kHz (Fig 1)
Using PSD vector as the matrix for NMF
decomposition
Decomposition ran for 1000 times; Retaining significantly different
basis between dolphin Core Habitat and Non-Core Habitat (p<0.001)
Figure 1. Spectrogram of all recordings from Core Habitat and Non-Core Habitat
Figure 2. NMF decomposition into 4 Spectral basis (Left Panel). Colours represent the relative contribution of that basis (y-axis) along each frame (x-axis) (Right Panel).
ACKNOWLEDGEMENTSOcean Park Conservation Foundation Hong KongCetacea Research Institute
Data Collection: 3-min acoustic sampling at 15 field
locations in Hong Kong waters across 2 years (2016-2018)
Figure 3. Spectral features from 1000 trials of NMF decomposition (25%, 50%, 75% of spectral features)
NMF Decomposition Result (50 %) as Prior Information(Labelled as
Important Spectral Basis and Other Spectral Basis) for classifying site-
specific marine soundscape composition with regard to dolphin
distribution
Figure 4. Relative Strength of Spectral Features in all recording sites
