Warrior · Fury · tier 1 · from level 10

Booming Voice

Rank 5/5

Increases the area of effect of your Shouts by 50% and reduces their Rage cost by 25%.

Doesn't change the damage or healing of any Warrior spell.

Averages, counting crits and misses, for a level 60 Warrior with a typical weapon and no other gear or buffs, against a target your level. Worked out from the game's own data, the same way as the Foresight addon.