Megaphone.

A megaphone is a cone-shaped device with openings on both the narrow and wide ends, enchanted to amplify your voice. While holding the megaphone and speaking through it, you can use an action to cast the Thaumaturgy spell at will, choosing only the effect, "Your voice booms up to three times as loud as normal for 1 minute."

Rarity

Wondrous Item, Uncommon