There's a kind of hum all over the world. But only some people can hear it. It turns out not to be aliens – though I don't see why aliens wouldn't hum as they went about their world-conquering. Sometimes it's from local factories, electricity wires, fridges, or in my case a nearby airport that emits a thunderous roar when they're testing engines. All these things hum officially and it's not hard to find the source, not as hard as tracking down the humming aliens. But in two-thirds of cases, there's no obvious cause, and it has been decided that if you can still hear the hum you're suffering from vicious-cycle over-sensitive hearing. I think we may be on the verge of a new syndrome.

You focus on the noise and then you can hear nothing else, says Dr Baguley, head of audiology at Addenbrooke's. He's running a trial – funded by the Department for Environment and the Department of Health – using 'psychology and relaxation techniques to help sufferers become less agitated and distressed by the hum'. Now this suggests to me that there is after all a hum, in the first place to focus on and in the second place to become less agitated about. What's wrong with people is that they can hear it. The doc is actually getting them not to mind about the hum, which is one way of dealing with an environmental nuisance. Sort out the inconvenient humans who complain with CBT and self-hypnosis.

The odd thing is that I've just bought a quaint electronic device that drones out white noise (or, if I let it, the crash of the surf breaking on the shore) to cover the sound of the local drummer, barking dogs and screaming kids in nearby gardens. What it does, now I come to think of it, is create a hum and if it's loud enough it almost drowns out the other sounds. I'd advise those attending the trial to give it up and learn to love your hum – there might be much worse noises out there if you stop hearing it.