Some mechanical keyboards are loud, but not all of them. My newest keyboard is a Kinesis Freestyle Pro with "Silent Red" switches. It is "mechanical" but quieter than my MBP. I am sharing a home office with my wife right now, and I was worried when I ordered the keyboard because she complains that my chair creaks and makes too much noise, but she was fine with the keyboard.

I have a CODE keyboard with brown switches at work, and putting dampers on all of the keys helped that quite a bit. My coworkers expressed some interest in that one, but no one complained.