How to go about Disconnecting annoying car alarm on 06 Civic Hybrid?

Alternatively to Pushrod's advice, your vehicle has a factory equipped anti-theft system that utilizes the vehicle's horn to indicate that a door has been opened without a key. It is possible one of the door switches have failed, indicating that the door is open erratically when it is actually closed. If you think about it, if the door suddenly shows as "open" while closed and locked, and no key or remote was used to disable this, then the control module thinks the vehicle was accessed inappropriately, setting off the horn. A diagnostic tool that can monitor body component data will show the position of door switches as open or closed and can be monitored to diagnose this concern.