radar does indeed beep when it detects something approaching fast (10Kph faster than your speed) but alerts are not carried through earpiece if you are connected to a phone... (sound of edge 820 can be…
I have a first generation Edge 1000. I believe that is the issue with mine. It may beep when a car approaches, but it is so faint, I could never hear it outside when testing. The Varia app on my phone solves the issue since I never ride without my phone. It also does not seem to use a lot of battery power on my phone.
I have the same issue with my new Edge 830, radar alert beeps are often too low to be heard...so I run RidewithGPS in my iPhone (11, and in a jersey pocket)) and the alerts are loud and clear with the volume up. The Varia can be paired to RWGPS in the RWGPS settings manu...