What does Heavy Armor Training mean by "only taking Health damage from sonic attacks"?

//ads -- adsterra.com -- native banner
?>
The description for Heavy Armor Training (SWAT level 5 perk) states:
While you have body armor, you only take Health damage from sonic attacks and clots can't grab you. You begin each game with 50% Armor.
However, the only thing that does "sonic attacks" are Sirens who have only done health (and not armor) damage since Killing Floor 1. What exactly does this perk do in terms of damage prevention?
Pictures about "What does Heavy Armor Training mean by "only taking Health damage from sonic attacks"?"



How to Actually Survive Being Stabbed
Sources: Stack Exchange - This article follows the attribution requirements of Stack Exchange and is licensed under CC BY-SA 3.0.
Images: Victor Freitas, Pixabay, Victor Freitas, Andrea Piacquadio