high pitch

Hello all, Apologies in advance for being completely thick about all this but I wondered if anyone could give me any ideas as to why the boiler has started making this noise. A google search tells me to keep an eye out for a low hum (kettling) but this high pitched noise hasn’t been described...

So not long ago I joined a "not so cheap health club" that also has a rather nice hotel. The other day I noticed that the hotel has a number of the following devices around it what appear to be around 4-6 meters off the ground. Now at first I carefully approached it, in case I was going to...