What is the purpose of all the different siren sounds on an emergency vehicle?

Question

Police cars , ambulances, and fire trucks all haves some crazy sounding sirens noises. Are they used for different emergencies or places or what?

Answer 1

Not everyone hears the same frequencies or sounds the same way. As your hearing starts to go bad, from listening to loud sounds and music for years, you don't hear the high frequencies anymore. They run the sirens up and down the range and stutter them with loud horn like sounds so they will, hopefully, get everyones attention.

Answer 2

To try and get the attention of other drivers.