It's high pitched and piercing. Thankfully I can't hear it in the computer room, as it's in the back of the house and there's enough noise in here from the computers that it doesn't reach. However, my bedroom is in the front of the house. I can hear it very clearly there.
I wandered outside to have a look, and as far as I can tell it's the security alarm on a house further up the road. At least if it was a car alarm I could theoretically call the cops and get it towed away. What's the use of having an alarm if it's going to blare away for an hour and nothing happens? It might make someone robbing their house deaf, but that's about it.
The chances of me getting any sleep while that's going is zero.
I now have an ache in the back of my neck, and another one growing above my left eye.