  This paper proposes multiscale convolutional neural network (CNN)-based deep
metric learning for bioacoustic classification, under low training data
conditions. The proposed CNN is characterized by the utilization of four
different filter sizes at each level to analyze input feature maps. This
multiscale nature helps in describing different bioacoustic events effectively:
smaller filters help in learning the finer details of bioacoustic events,
whereas, larger filters help in analyzing a larger context leading to global
details. A dynamic triplet loss is employed in the proposed CNN architecture to
learn a transformation from the input space to the embedding space, where
classification is performed. The triplet loss helps in learning this
transformation by analyzing three examples, referred to as triplets, at a time
where intra-class distance is minimized while maximizing the inter-class
separation by a dynamically increasing margin. The number of possible triplets
increases cubically with the dataset size, making triplet loss more suitable
than the softmax cross-entropy loss in low training data conditions.
Experiments on three different publicly available datasets show that the
proposed framework performs better than existing bioacoustic classification
frameworks. Experimental results also confirm the superiority of the triplet
loss over the cross-entropy loss in low training data conditions
