In a film without Jedi, it’s interesting to see how much of a role both kyber and the Force itself still played.
The symbolism of Chirrut having a sliver of crystal in his staff is interesting, too, especially since some had speculated at one point that the “lamp” may have been a lightsaber component.
Listening for sounds made by enemies (as showcased in his first fight scene) provides him with a target that he can then drive the staff toward.
The idea that he can hear the harmonics of kyber crystal also explain him knowing that Jyn was wearing a necklace, since he could hear the crystal on the necklace itself.