What is the sound of a ambulance?

It depends on where you are in the world. In the US, most ambulances sirens have 2 or 3 settings....a long, slowly ascending and descending Whooo sound, a short rapidly ascending and descending warble tone, and sometimes a 3rd, higher, louder, phazer sound (my favorite to get attention of complacent drivers). Rarely, US rigs will have a European, up/down, British, DA/da/DA/da/DA tone. We have 1 rig at our department with the rare European setting. I love to use that setting through intersections here in the US just to mess with people, because most Americans have never heard that tone, except in movies. Ambulances in the US also have either a genuine air powered horn (awesome), and/or an electronic simulated air horn sound (lame). If you pay attention, before long you will able to tell the difference between police, ambulance, fire engines, and personally owned emergency response sirens just by the subtle sounds of each siren. The loudest, best siren is the air powered siren on the Fire Engines. They are controlled by a foot button located on the floor of both the driver and passenger/officer seat of the engine, an air pump, and a big, loud, steel speaker horn. They are easily the loudest siren available. Some police cars in the US have a "Rumbler Siren" that bottoms out at a subsonic level to send shock waves into the ground and surrounding areas, so that even if you have a crazy loud stereo cranked up in your car, you will feel the police siren in your bones....pretty cool. Ambulance sirens are usually between 100 and 200 watts of powered sound, and about half of the drivers on the road are completely oblivious to both lights and sirens until you are really close. When you see emergency lights behind you with a siren in America, pull to the RIGHT and stop. They will always pass you on the left in the US. If it a cop, you will notice blue lights. It is very rare for any other emergency vehicles to employ blue lights in their ensemble...and usually illegal. If an unmarked police car attempts to pull you over, call 911 and verify the identity of the unmarked car before pulling over, or drive to the local PD if it is close. Although illegal, it is not hard hard to obtain emergency lights in the US, and is a tool used by criminals to pull over victims. Rare, but it happens.