Visualizing Directional Soundscapes of Bird Vocalizations Using Robot Audition Techniques

A visualisation of the soundscape dynamics is one of the important topics in ecoacousics. However, existing approaches mainly focused on the soundscape in the frequency domain while the soundscape in the directional or spatial domain is also essential to better understand animal vocalizations. This paper proposes and discusses novel applications of robot audition techniques to visualize soundscape dynamics in the directional or spatial domain by using the directional information of sound sources obtained from the robot audition software HARK (Honda Research Institute Japan Audition for Robots with Kyoto University) and the software for birdsong localization HARKBird. First, we create a false-color spectrogram that visualizes directional soundscapes in which the color of the spectrogram reflects the direction of arrival of separated sounds. We also visualize the distribution of directional soundscapes by combining the entropy of the likelihood of sound existence (MUSIC spectrum) and a latent space embedding method (UMAP). We applied these techniques to a 5 min recording with 6 individuals of Zebra Finch in order to show that the extracted visual information can reflect acoustic structures among the group of bird individuals in the directional domain.