Airpods don't work properly when outside

I have Airpod Pro's that I've had for a little while now. They work completely fine when I'm inside my home, or say if I'm on a bus or a train. However when I walk outside they are terrible. The Airpods don't disconnect, but the sound continually goes on and off, therefore I don't use them outside because the audio I'm getting is just so poor. Does anybody have any ideas why this might be? I live in a big city with signal everywhere which was my first thought. It's so frustrating being unable to use them outside whilst seeing everybody else walking around with them! Any help would be greatly appreciated.