Onsei Kakudai

Onsei Kakudai (Japanese: 音声拡大おんせいかくだい Romaji: onsei kakudai, translated as Public Address System) is supposed to be an air shamanistic spell. This is not the name of the spell, merely its function, the Power Words are unknown.

It allows the caster to amplify sound in a particular area. Speech becomes much louder and can be heard from far away, hence the spell's name.