It is a really loud, 80 dB speaker.
Wyze Battery Cam Pro has a speaker inside that can be used as a siren to ward off intruders.
To control the Siren feature:
In the Wyze app, tap on your Wyze Battery Cam Pro.
Under the live stream, tap Siren. (Be careful, it’s loud!)
To turn it off, tap Siren again.
Can another device trigger the Siren?
Yes! You can do this via Rules (specifically Device & Service Triggers) in the Wyze app. You can learn more about using Rules with Wyze Battery Cam Pro here.