Hi @toch,
There’re multiple ways to do this. My first suggestion would be to first create a group of your sensors with the group app. Which can be found here: < groep > App voor Homey | Homey
Create a group of your sensors
Then create a trigger that if the group sensor go in alarm you active your sirene
Another thing which would be good to explore is the heimdall app. Which is a very comprehensive security app with a lot of build in security and alarming features without you having to build to much flows
At the link below you can find more information on the configuration and features of that app
