The “Ring Splash” ringtone is intended for situations like automatic forwarding where you may be interested in knowing your extension received a call, but don't intend to answer at that location.
For example, if you forwarded your line while you were at lunch at your desk you would hear the "splash" and the call would be forwarded on. The single ring is by design.
Note: Be sure when changing ring tones, to thoroughly test and ensure the ring tone meets your business requirements.