Have the announcer say "Your turn to pick/ban" when it's your turn to pick/ban
Similar to what they do in DotA 2.
http://hydra-media.cursecdn.com/dota2.gamepedia.com/4/40/Announcer_pick_yr.mp3
http://hydra-media.cursecdn.com/dota2.gamepedia.com/0/0e/Announcer_ban_yr.mp3
As of right now, the ONLY audio prompt we get is at the ten second mark where we get a little "beep" and that's it.
If that isn't feasible, just have it work like the old champ select, where your client automatically focuses in and makes a noise that is louder than what it currently makes at ten seconds.
announcer pack only to completely remove it from the game Q.Q