This page includes all of the specific details of the selected feat as well as the Section 15 entry of the OGL for the product from which the feat comes. Feats listed in the Prerequisites section should be linked as well.
Altering a spells sound is the first step on the path to silent casting.
Ability to cast spells.
Changes the sound a spell makes when cast, causing a -2 penalty to spellcraft checks to idetify the spell. So an electrical spell could sound like water, or a unidentifiable creatures roar.
The volume of the sound stays the same. Speech is not possible with this feat, neither is a specific creature, the sound is rather chaotic.
A spell affected by this feat uses a spell slot one level higher tha the spell's actual level.