The low frequency noise, which only a tiny minority of people can hear, creates a din so loud that it is almost impossible for those who can hear it to block it out. Simon, who lives in Little Paxton, even moved house to try to escape the noise comparable to the sound of a distant diesel engine idling but he could still hear it. Whenever he travels, even abroad, he may be clear of it for about a day or two and then his hearing will tune into it again. He now cant get by without resorting to sleeping pills, which he said he is now addicted to, because he said that the only way to block out the sound is to knock himself out. It has completely ruined my life, my health and my career. I have lost most of my friends and as a result become really isolated, Simon said. Aged 50, he said it is very rarely a sound that is heard by younger people, who traditionally can hear much higher frequency sounds. It was in 2006 that he first began to notice the hum, which he said is louder inside buildings and which he maintains has got louder. When I first began to hear it, what alarmed me is that I just could not identify it or block it out either. But I have been determined to try to get to the bottom of it. For me there is no doubt in my mind that it is a worldwide phenomenon and what is causing it I dont know, but I have my theories. His doctor, who has said there is nothing wrong with his hearing, wanted to refer him to a specialist at Addenbrookes Hospital, Cambridge, not because there is a cure, but for cognitive behaviour therapy to teach him ways to cope with the sound. He called in Environmental Health which managed to capture the sound using sophisticated equipment. However it is difficult discern because it also picks up every other tiny sound in the house. But Environmental Health was perplexed as to the source of the sound. Simon is not alone as tens of thousands of people across the world say they can also hear the hum. Most people cant hear it so those who can are considered to be a nut case or delusional. I am not interested in claims that it may be an alien and conspiracy theories, or any of that nonsense. I am a rational person, an engineer by training and not given to flights of fancy, but I simply cant believe I am the only person in the area to have heard this noise every night for years on end. Although it is recognised that the hum is a low frequency sound that certain people can hear, its source remains a mystery. I feel that only exposing this as a serious public health issue will force governments to act and investigate it properly, he added. Simon has his own theories about the source of the sound. He believes that it could be as a result of fracking, hydraulic drilling deep underground at the Earths crust taking place as the government looks for sources of shale gas. We all know that sound can travel huge distances through water, and I believe it is the same through the earth beneath us. The hum seems to propagate through buildings and gets louder inside. The amount of energy fracking uses is colossal and vibration travels a long way through the earth. The sound is definitely man made, he said. Simon added that although there was no real pattern to the sound it can start around 10.30pm and last all night. Whenever I wake up it is there and it is unbelievably loud. When nobody else can hear it around you think you are going nuts and it just wears you down. I have been desperate to get away from it so have stayed with friends and even moved house. It goes quiet for a day or two and then starts again. I am lucky that my partner is kind and accepting of it and is very sympathetic. There have been reports of the sound in newspapers throughout the UK, particularly in the south of the country, and across the world. The Hum Forum has been formed and is devoted to discussion about the noise, which they said is heard by one to 10 per cent of the population in certain areas. Simon wants to hear from other sufferers so that a local lobby can be formed to push for research in the hope that those who are suffering do not continue to do so in silence. Simon can be contacted via firstname.lastname@example.org. The Hum Forum can be found at http://groups.yahoo.com/neo/groups/humforum/info. The World Hum Database and Mapping Project can be found at www.thehum.info.