[qball]

>This means that when the actual (very loud!) crash happens, your hearing is saved.

The loud part is not the crash itself, but the airbag deployment; it's as loud as a rifle shot because, fundamentally, it is a rifle shot. That's bad in open air; it's way worse in a confined space where that pressure is going to persist for a much longer period of time.

The combustion gas needs to fill the airbag coincident with your face being mashed into it at high speed, and mechanical suppressors slow down the gas so that won't work; using the acoustic reflex (as Daimler clearly does) to get that extra 15 dB of protection means the difference between maximum safe exposure and permanent damage.

I'm surprised that this sound doesn't start playing right before the similarly-explosive pretensioners are fired, since they're also pretty loud, but perhaps they figure it's part of the way to prompt the reflex.