Water can do strange things with sound. The Chinese may have picked up pings in a manner not entirely unlike picking up a radio station well beyond normal reception range only to have it suddenly fade away.
In the atmosphere, one phenomenon that can cause that is called “tropospheric ducting”. It happens when layers of air stratify creating a “duct” that directs the signal, much like a wave guide used in microwave radio transmission. I recall traveling through northern Louisiana once on my way to Alexandria, LA, to work on a cellular system. I was picking up a Colorado Springs, CO, FM station 900 miles away for about 30 minutes. Various densities of salinity and temperature cause sound to behave similarly in the open ocean.