I allways thought that is required part of the spellcasting. O_O
Surely a normal speaking voice is enough even if a whisper might not be. The shouting just seems to be for show and it feels wrong in most cases. Sure, shout a Fireball that creates a roaring fiery explosion anyway but casting a cantrip should not require that much volume.
If Larian's vision is that the verbal components need to be shouted even for cantrips, they should make enemies react to the sounds and come investigate at least. But I'd much rather hear something more subtle. BG1&2 got this right. Spells sounded really cool even in a low voice or whispered. They used echo effects and other sound effects combined with the words.
