The alarm module has 2 batteries in it that give up causing the 'cricket on crack' sound.
The module is located in the center under the plastic windshield wiper cowl cover.
You have 3 choices :
1. if the batteries haven't leaked and corroded the circuit board, you can do the fix to replace them.
2. get a new alarm module from a dealer, or get a MB module on eBay.
3. unplug the alarm module.

Do a search for alarm module and you will see countless threads addressing this issue.