Bio-duck and bio-goose: Mysterious sounds from the Southern Oceans

This paper revisits recordings of curious sounds that were heard in waters around Australia and New Zealand some years ago. The sounds provided the New Zealand surveys were recorded on a low-frequency towed horizontal line array operating in the South Fiji Basin. They were thought to be generated by marine animals at distance from the array, but the type of creature was not identified at sea or in subsequent analysis. Owing to the limited bandwidth of the recordings, the sound was accordingly dubbed as Bio-Duck. Similar sounds recorded with higher bandwidth in Australian marine surveys were called Bio-Goose. Further characteristics of the sound waveform and spectrum are presented, along with evidence of a probable conversation between several speakers.