Turn off Droid4 boot sound

I have a Droid4 that has a dead battery. I got the replacement delivered today.

On the old Droid4, I was able to disable the machine from saying "Droid" upon startup. Now I have a replacement Droid4 and I don't remember how I did it before. I know I didn't do any filename changing or other root things because I don't know how to do any of that on a Droid. I'm sure I stumbled upon it in a menu path somewhere. Where could it have been? Some bulletin boards suggest turning off System Volume. I go to System Settings > Sound > Volumes and there are only 4 slide bars: Music,video,games,&othermedia; Ringtone; Notifications; and Alarms. There is no slidebar for System Volume. I know I had it fixed on my old Droid4 but even after I fixed it, I couldn't find it again to tell my friend how to fix hers. Where the heck was it????? Thanks, Sue