Can you see a blinking light on your dash by the middle of the windshield when locked? Does your keyfob have a red panic button on it? If the answers are yes, then you have an alarm. Also check for a round siren at the middle of the firewall behind your engine.
Alarm covers all doors and the hood. There were also some other oprional sensors
from Volvo like a glass breakage sensor and a tilt sensor. For Euro markets, they
also have a 2 stage, deadbolt locking system for all the latches. More here:
Leave a window open and reach in and open a door a few minutes after you lock up.
It should flash and honk the single horn on the firewall. Then get out a wrench to tighten
up the center nut of the horn. It's probably gonna sound like an asthmatic duck...