A whistling radiator
I've had a gas man working here today, fitting some new radiator valves.
When the heating came on at tea time, Inlticed one of the kitchen radiators was making a horrible high pitched whistling sound, a bit like the old kettles that whistled when they were coming to the boil, but not as loud as that.
It perhaps wouldn't bother some people, but my ears (and nose) are very good, and this noise bothers me, it seems to get right down in my ears. It didn't do it before today, so presumably its something to do with the new valve.
Any ideas what could cause it, and can it be stopped, because it will drive me nuts if it carries on.