There are various bings and sonic events that happen on flights, landing gear up, landing gear down (which also illuminates the exit signs), the sound made by the call bell, there's a sort of "vrruup" noise you can hear at the front when auto-pilot on an airbus is disengaged. Also the tone of the engines, you hear a lessening when about to start the descent. BA ring a bell when about to enter an active runway when taxiing, and so on.

If you're a nervous flyer, as many are (perhaps including the OP) these can be disquieting, and it's worth knowing what they are. Once you can anticipate them you can actually use them to be aware of which phase of flight you're in, which provides a structure that can reduce anxiety.