why does rain sound like broken glass in the crystal empire?

(this post is in an alternate timeline) crystal cover half of the are and the other half lays destroyed after a civil war happened years ago when king sombra was young. steam hoof was a inventor until a biocrystal test gone wrong ended his life now, he goes by the name of crimson rain. crimson over the years has gain a few abilities including the ability to make an illusion that trick most into thinking he is what he want to be, crystal manipulation, and crystal absorption. crimson was in a building as polo walked in then, crimson stopped moving as polo said "hello anyone here?". crimson kept still until polo was an inch from him then, he cover polo legs in crystal binding him into the ground and said "who are you and why are you in the bad part?". "i honestly was hoping to find a book to get out of this timeline" polo said as crimson hold a dagger an inch from polo neck and said "don't lie to me stranger, now talk about how you got in without the guard noticing?". polo looked at crimson and said "there was mining system so i traveled using that". crimson released polo and said "get out of here, this place has nothing to look for". polo nods and walked outside as it start raining. crimson watch from a window and said "feel like i meet him before". a few hours go by before polo wakes up as his body color darkened a bit and said "weird". polo heard a guard behind him then, he duck as a spear hit the mirror. "by..." before the guard could talk polo tacked him and proceeds to remove the mask causing the guard to forget everything. polo grabbed the helmet and spear and said "talk about a boring fight, i might need to work on the helmet in order to sneak into the castle.". polo walked out of the house and watches as the rain falls.