Changing startup and shutdown sounds Is there any way for me to play certain audio files when my phone starts up and before it shuts down?

I have a Samsung S3.
Root your phone with Kingo root. 
Use a root browser, like ES File Explorer, to find the the file (probably mp3, ogg, or wav) and rename it to have .bak on the end. 
Paste your sound in the same spot and name it what the original used to be. The file could be under /system/media/audio/ui or under/etc/ called something obvious like PowerOn.mp3. I'm not really sure where Samsung put the file. 
Go into the SuperSU app, under settings you can choose to un-root your phone. I think you can also un-root by plugging your phone back into the computer and use Kingo. 


There are many advantages to rooting though, like Linux Deploy and wipe-proof avast!. Or even remote control through AirDroid. It's safe as long as you don't mess with system files you don't know about or give SU privileges to apps you're not sure of.