The truth is that most car thieves don’t waste their time trying to jimmy your lock like you see on TV. Just like any other “professional,” they recognize that time is money, so they’re just gonna bust your window in. A car thief, who knows his stuff, can drive your car away in only a minute, so before anyone even thought to dial the police - “Was that glass breaking? Just now, outside… didn’t you hear it? Maybe I imagined it. No, I couldn’t have, let’s call 911 and report it” - well, that car has already been driven through half a dozen red lights.

The car which is equipped with a pressure sensor can start wailing even before the first shard of glass hits the pavement. A glass-breakage detector is merely a simple microphone which is connected to the car’s brain. The microphone measures the variations in air pressure fluctuation, and then converts that pattern to an electrical current. Only when the fluctuations are identical to glass breaking, which has a very distinctive pattern, does the alarm trigger. And that’s a good thing, because you don’t want the car alarm to be triggered merely by passers-by.

Another type of pressure sensor recognizes any difference in air pressure inside the car. So, if a window is broken or a car door is opened, the air pressure inside your car is altered, and that triggers the alarm. Of course, if you regularly forget to close your windows before you get out of the car, then this is not the alarm system for you.

Both types of alarms either have a hidden switch mounted somewhere near the dashboard, and can be turned on or off before you get into the car. You’ve only got about 10 seconds to deactivate it, though, so if you forget and it starts while you’re driving, hold tight to the steering wheel.

Now these alarms may not deter a professional thief who can probably disable the alarm pretty quickly (if he finds it pretty quickly, that is), but the average joy-riding teenager will think twice before he gets behind the wheel of a car with an alarm wailing. Unfortunately, at that point, enough damage may have been inflicted on the car to cause you a bit of grief. But at least, the car will still be where you parked it.