Good for you, shanghai. (May I call you shanghai?)

The cats are probably objecting because the bodhrans are too loud. For some reason, a cat which is bothered by music doesn't just leave the room. Oh no! The cat must stick around, registering its disapproval. It's something to do with the fact that they are actually the bosses of the house.

If I were you, I would just put the cats in another room and close the door. That way you can practice without worrying that you are hurting them.

I shared a room recently with a cat who objected to my flute playing. Philistine!