Yes, this is easy via the app. There are 3 options for the siren.
Download and open the App
Go to Settings Go to Siren (Settings) 1. Choose 'Loud' and confirm with 'Ok' 2. Choose 'Low' and confirm with 'Ok' 3. Choose 'Mute' and confirm with 'Ok'
The notification via the mobile network does not depend on the volume of the siren.