If a police officer is not capable of maintaining their cool and issuing clear commands relevant to the context they're in, they shouldn't be issued a lethal weapon in the first place; a recorded voice shouldn't be a replacement for this, and might just add to the confusion of voices and noises, and wouldn't have understanding of the specific situation (until we get to robocop level AI)

The strobe idea might have some merit for the deaf, or folks who don't understand the local language, so long as there is a long standing education campaign.