On the 850 at least the alarm horn is in the center of the car under the hood in front of the cowl. You could pull the plug out of it. Doesn't the alarm also cut off the ignition or otherwise immobilize the car though? Why does yours ever ring at all?

I was the victim of the one crime that marred NH's otherwise entirely pristine history. Went hiking for several days in the White Mts. Parked car at a trailhead not far from Gorham. When I came back the drivers door had been pried almost all the way off the car and nothing was left inside. An alarm wouldn't have helped if I had had one.