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Oh, Lordy.

As mentioned, spend time shooting, as much as you can with handguns and long arms.

Without a suppressor or muffs, I would be disinclined to recommend a rifle. If you wonder why, have a "friend" hold a toilet plunger cup in each hand, and clap them over your ears, as hard as they can, and see if you feel that you'll be well-oriented to what's going on around you, immediately afterward. Short version, if you've done it before, you know what you're up to, if you haven't, an urgent situation is not the time to start.

Handguns. 9mm or .45 are probably better choices. Again, without hearing protection, revolvers disperse more gas (and noise), and stepping up to .38+P or .357 mag is pretty harsh.

Some will claim "auditory exclusion" will get you through. BTDT, no it doesn't. An indoors concussion may not make you flinch/miss/whatever, it does stun you and slow your thinking. All the things that make our homes pollen/bug/water resistant keep sound inside very effectively. If you have tile, linoleum, laminate, wood or tile floors, it's rather unpleasant.

Shotguns are good indoors long-arms because their muzzle blast is not as high pressure as a rifle. They are generally less expensive, which is nice if it has to be retained for evidentiary purposes, and are generally more socially acceptable, in addition to being HIGHLY effective using relatively cheap ammo.

If you decide to settle on a rifle caliber, without using a suppressor, one of the linear compensators (Kaw valley, Hera, Levang, or similar) helps a whoooole bunch.