There are also some other ways to convert audio to iPhone ringtone and sync it to iPhone with iTunes, but I think these are a little complicated and users may be at a loss with such ways.
Here I recommend iPhone PC Suite, an almighty iPhone manager that can let you manage phone book, software, media and other files between iPhone and computer without iTunes easily.
But before using this tool, make sure your iTunes installed and has been connected with iPhone once before (Then you need not run iTunes when you use iPhone PC Suite to manage your iPhone).And when the first time you connecting iPhone, it will install PhoneDaemon on your iPhone, don't worry it is green software and will do nothing harm.
Now I will show you how to sync the converted iPhone ringtone to iPhone without iTunes. Connect you iPhone to computer, double click" iPhone PC Suite" to start iPhone PC Suite, the program will scan you iPhone automatically for a short while. Then click button "Personal" on the main menu, select "ringtone".
Click "New Ringtone" to locate the converted iPhone ringtone.
Select your target iPhone ringtone, then it will upload the ringtone to iPhone automatically.
Then you can select your favorite audio file and set it as your iPhone ringtone on iPhone. Click "setting"->"Sound"->"Ringtone", the converted ringtone is listed on column "Customize". Now you can enjoy the fun of your unique iPhone ringtone!
This free iPhone PC Suite also has other powerful functions, we will share them later.