So my cat wakes up at 5am, like clockwork. And we have figured out what it is, we live in an apartment above a gym, and somebody goes to gym every morning at 5, making noises that wake up the cat. I've tried putting on music throughout the night to drown out noise and that doesn't seem to work either. It's driving me insane. I don't know what to do! :( it's been months and she won't get used to it to just sleep through it.

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I'm guessing that when your kitty hears the noise, it is time for the entire household to get up! Unfortunately, this is not going to away as long as someone is in the gym at 5 a.m. Moving to another apartment could be an option, putting down heavy rugs to abate the noise is other option. Try using white noise (from a sound machine or app on your phone) and see if that helps.

Or ... you can hope that once the gym's lease is up, they relocate. A cat's hearing is so much better than ours, so your kitty can hear noises you can't. Do not blame your kitty. Mine is ready to get up at 5 a.m. as well.

There's nothing you can do to mask the noises a cat could hear. The only successful option would be for you to change the apartment.

However, note that:
1) most cats wake up early. So it could be that your cat wakes up early because of the season or so.
2) moving to another apartment may not get your cat back to sleep late immediately. You wrote it's been months, so her routine has changed and would take long to readjust.