From Dota 2 Wiki
Announcer items are cosmetic items replace the voice responses of the default announcer. They can equipped in the loadout window. Like HUD Skins, Announcers can be shared with team-mates through the Shared Content panel.
- Announcer Packs replace all lines, except for killing spree lines.
- Most custom announcer packs have more lines than the default announcer.
- Mega-Kills Packs replace killing spree lines.