You can “toughen up” your ears by continued exposure to loud noise.
If you think you have grown used to a loud noise, it has already damaged your ears. When noise is too loud, it begins to kill the sensitive nerve endings in your inner ear. Remember, there is no way to restore life to dead nerve endings; the damage is permanent. Consult an otolaryngologist for appropriate hearing protectors if you work in an excessively noisy environment, or use power tools, noisy yard equipment, or firearms.