I can hear loud ringing noises at night time which keep me awake. Is there a sub-station or similar nearby? The noise sounds industrial, and rises and falls.
Noise like this can be caused by a number of different sources. Possible explanations might include some sort of electrical energy source or mechanical output. However, be clear about how you describe the noise – is it a “ringing” (high pitch) or more of a low frequency hum.
Ocassionally tinitus can be a problem for some sufferers and can be mistaken for an external source (particularly in older folk). The noise you have described may fall into that category. If so, you may wish to talk to your GP.
I would suggest that you exclude any possible cause related to your own home first (by turning off your mains supply, for example). Once this has been ruled out completely you could go to your environmental health department and request they look into it. Some departments have a soundmeter that helps them to track down the source of a distant noise. If not, one of their colleagues from a neighbouring borough can help them do this. If you can have a look around the neighbourhood yourself try and identify the source as well.