Let's address the quite varied questions individually:
If someone knows my wifi password (be it WEP or WPA) what kind of
control do they have over radio waves?
Next to none. If you've not secured your router, they might be able to change the channel that your Wifi uses, but you need some fairly interesting equipment to do anything outside of the standard wifi spec.
Can they emit radio waves from computers on my network? What about
Simply put, no. They have access to your devices the same as they would if they plugged a network cable in. Unless they have some undocumented vulnerabilities, that fairly severely limits what they can do.
What kind of access would they have to a X Box 1 camera?
As far as I know, the Xbox 1 is not vulnerable to any attacks either from the network side, or man-in-the-middle. So, none.
Would there be anyway for the hacker to use it if the XBox was
No. If there's no power, and no connection, there's no threat.
I guess what I'm really trying to figure out is can/could a hacker
transmit radio waves that are audible, but just barely to a person?
No. Radio waves are not, and will not be audible. They move different things to sound waves.