My upstairs bedroom has carpet flooring but i am hearing loud cracking noises like if someone is walking on the floor but know one is there can the wood that's underneat make cracking sounds like that?

The most logical explanation is a ghost. If you're house is old it is most likely harboring tons of spirits, if you've just moved in, think about recently deceased relatives or friends. Could one of them have a message to tell you? Was a friend/relative angry at you before they died? If so, try politely speaking to the ghost, ask him/her to kindly leave you alone or ask him/her to tell you why he has come to you. Still not working? Try a seance. Remember to never become angry with the ghost, always stay calm and open minded. Still not working? Your last option is exorcism, call in an exorcist to get rid of your ghost. I had a poltergeist and could not get rid of it once, no matter how many seance's i did that poltergeist wouldn't let go. I called an exorcist and BAM! Haven't had a ghost problem since!

Or it could be the normal expansion/contraction caused by heat gain/loss.