Archetypal analysis based sparse convex sequence kernel for bird activity detection

This paper proposes a novel method based on the archetypal analysis (AA) for bird activity detection (BAD) task. The proposed method extracts a convex representation (frame-wise) by projecting a given audio signal on to a learned dictionary. The AA based dictionary is trained only on bird class signals, which makes the method robust to background noise. Further, it is shown that due to the inherent sparsity property of convex representations, non-bird class signals will have a denser representation as compared to the bird counterpart, which helps in effective discrimination. In order to detect presence/absence of bird vocalization, a fixed length representation is obtained by averaging the obtained frame wise representations of an audio signal. Classification of these fixed length representations is performed using support vector machines (SVM) with a dynamic kernel. In this work, we propose a variant of probabilistic sequence kernel called sparse convex sequence kernel (SCSK) for the BAD task. Experimental results show that the proposed method can efficiently discriminate bird from non-bird class signals.