It can certainly be a rattling experience for drivers, when they suddenly realize that the sound of an emergency vehicle's siren is coming from someplace nearby. Cerence's EVD system is designed to help, by hearing sirens before drivers do.
Cars are equipped with loud electric horns, not little bells, as are motorcycles. So, why isn't this the case with bicycles that get ridden in traffic? That's the thinking behind Sonic Grip, which packs a 100-decibel siren into a bike's handlebar grips.