Displacement = the greater the displacement of the LDC the longer time it will take for the air to exit the muzzle spreading out the sound energy over a longer period of time. So displacement is directly related to delay.
Dampening = absorbing sound energy converts it into heat energy, reducing the muzzle report. Sound waves impinging on an object are either reflected, absorbed, or transferred. In most real life cases a combination of all three occur. The more sound energy absorbed lessons muzzle noise. This is where felt, foam, fiberglass, etc come into play. Aluminum and steel tend to transfer and reflect a lot of sound.
Delay = Anything you can do to slow the exit of gasses from the muzzle lowers the peak sound level but will extend the lengthen the muzzle report. Delay also importantly allows more time the gasses stay inside the gun so more sound reflection and absorption occurs, converting sound energy into heat. This is where baffles and displacement come into play.