Air pumps are often pretty loud. You might be able to spend a bit more than normal and get a 'silent' one though.
How long have you had the tank? If it's the filter that is noisy that should get quieter with age.
Tbh, I'm used to the sound of air pumps and filters. I have 4 fish tanks in my room, one in the hall and two in the living room. You won't mind the noise after a while.