After hooking a Survivor, THWACK! activates:

The next time you break a Breakable Wall or a Pallet, all Survivors within 28/30/32 meters of your location will scream and reveal their Aura for 4 seconds.

You reduce the duration of pallet stuns by 50percent.  Has no effect while carrying a Survivor.

The Auras of Survivors, who are healing or being healed, are revealed to you when they are within a range of 20/24/28 meters.

Survivors within your Terror Radius suffer from inefficiency:

When using an Item, its Depletion rate is increased by 80/90/100 percent.