A cat's eardrum may be ruptured in the following ways:
1. Observe the cat's ears for bleeding or discharge. If so, it is very likely that the eardrum has ruptured.
2. Gently touch the cat's ear with a cotton swab. If the cat reacts violently, it may have a ruptured eardrum.

3. Take your cat to a veterinary hospital for examination. The veterinarian can visually determine whether the cat's eardrum is ruptured.
The above are methods for determining if a cat's eardrum is ruptured. We hope this information is helpful.