Mine is very sensitive, just with the keys in my pocket at work. It caught me a few weeks ago at work. I forgot I had the keys on my belt, and when I sat down, it went off. I sat on my keys (felt like a moron). I just hear car alarms all the time around here, that nobody pays them any attention anymore. But, like you, I had never heard mine, so it threw me off, but, it must not take much.