The sounds of the Yangtze River finless porpoise, Neophocaena phocaenoides, fall into two main categories: high frequency pulsed sounds and low frequency time continuous signals. High frequency pulsed sounds might be used for echolocation, and low frequency time continuous signals related with communication and emotive state expression. When the animals were in normal situation, emission rates of both sounds were higher in night time than those in day time.
Wang Ding.A preliminary study on sound and acoustic behavior of the Yangtze River finless porpoise, Neophocaena phocaenoides,Acta Hydrobiologica Sinica,1996,20(2):127-133
