When champions are cloaked by the brush, but are still hit by his E, it makes the same whiff noise as if he just plain missed them. I don't know for sure, but I think this also occurs if they are cloaked.
Hearing the "you have just devoured a unit" noise is essential, since if I missed my slow as they run into the jungle it means they either barely missed or have used an escape. If I hear the whiff, I have to decide whether or not to spend 100 (or more) mana to chase them with Riftwalk. If they were hit and I wasted the cooldown, the mana, or just increased the cost, I am potentially ruining a clutch kill or escape.
So please, for the children, let me hear my normal sound effects if I hit someone through the brush with Force Pulse. <3