But it also dulls our receptiveness to real sound.
The car backs up: It generates a beeping that is like every other danger-beeping. It does not encourage us to pay attention, but rather the opposite. It happened to me just the other day. (In fact as I write this a most annoying beeping is wreaking its auditory havoc on an otherwise gorgeous morning.)
It is the automatic quality that disturbs me. Generating the noise automatically makes the hearing automatic, also; and by extension, the hearer.