The procedure is similar to the one I posted in the second part of my tutorial on modifying Sprint ROM's where you can make whatever notification sound you want part of the system (notification sounds folder doesn't have access to custom ringtones like the phone ringtones folder does in system/media/audio). In that same file location, besides the notifications and ringtones folders, there is a folder named "ui" which contains the various touch sounds (screen touch, several keyboard touch sounds, etc.). Once you have the .ogg file you want to use (like the one I am going to upload), you rename it to match the file name of the sound you want to replace. The one for screen touch sounds is called Effect_Tick.ogg. Using ES File Explorer to copy and paste, just replace the undesired one with the desired, renamed one, accept the warning message about "file name already exists." You don't need to backup this specific file as long as you have a ROM backup, as flashing the backup will revert all system-oriented files to what they were. Last step is to reboot phone, and then new sound will be applied.