The audible chirp when my XV Crosstrek is locked or unlocked is quite annoying -- worse is when someone hasn't closed the door completely yet and it beeps 5 times. Here's a simple (and completely reversible) way to disable your Crosstrek's lock/unlock sound. This guide also works for other Subarus (including the Outback) of the model year 2013+.

Note: You can still make your car "chirp" (though it uses the horn) by pressing the button on your remote three times. This is handy if you want to locate your car in a parking lot, for example.