The “Bristol Hum” – has it returned to plague the city? 

It kept people guessing for decades and was a mystery that was never solved – but now it sounds like the famous Bristol Hum could be back. Back in 1979 the mystery rumble that had half the city complaining made international headlines and led to a series of inquires and dozens of theories.

According to some it was triggered by power lines, while others blamed the M32 but one of the most popular theories was that the noise was caused by industrial fans at a warehouse in Avonmouth.

Colin Davis, who lives in Westover Close in Westbury-on-Trym, is convinced that the Hum is back in a new form – and says he knows what is now causing the infuriating noise.

The 50-year-old, who works for a business consultancy firm and shares his home with his partner Janie Abrahams, says the constant humming keeps him awake at night. He believes the problem started when new wind turbines were built at Avonmouth and has contacted the city council to complain about the incessant buzzing.

He said: “It is like a low hum that comes and goes, and it can be really annoying. It is keeping me awake at night and the worst thing about the whole thing is that it has really disturbed my sleep patterns.

“There were a lot of theories about the Bristol Hum but there was one report from two Oxford scientists who identified the source as a large industrial fan emitting low frequency noise.

“The fan was at the Shell site in Avonmouth and when it was decommissioned the Hum mysteriously disappeared, for good.”

Back in the 1970s complaints came from Clifton, Redland, Westbury- on-Trym, and most people affected lived on the top of hills rather than in valleys.

The phenomenon is apparently caused by low frequency noise which penetrates buildings and harmonises within the confined space of a house to create a hum.

Mr Davis said: “About one in 50 people can hear it and it is a completely annoying noise that won’t go away. In the 70s there were suicides and numerous people driven to distraction over this.

“After living in my house for over 13 years, in one of the quietest areas of Bristol, we now have a hum.

“I have strong suspicions it is being caused by the new wind farm recently erected in Avonmouth. The timing of the hum matches the commissioning of the turbines.

“The prevailing wind is in exactly the right direction and the sails point in exactly the right direction. As part of planning, the owners of the fans had to ensure there was no effect on the radar at Filton airfield. I am told this would have been the effect of low frequency noise generated by the turbines.”

Research has been carried out into the phenomenon by the wind industry trade association RenewableUK.

The study was carried out to investigate the causes of the low level noise known as “Other Amplitude Modulation” or OAM.

The report claims there is a differ- ence between “Normal Amplitude Modulation”, the common swishing sound made by turbine blades, and OAM, which is an infrequent and uncommon sound which usually lasts for a few minutes.

The organisation’s deputy chief executive Maf Smith said: “It’s right that the wind industry should take the lead in investigating issues like this when they arise.

“As a result of the in-depth research we’ve commissioned, we’ve identified the causes of OAM, and, most importantly, the industry has identified a way to deal with it effectively.

“On the limited and infrequent occasions when OAM occurs, we can address it by using software to adjust the way turbines operate, changing the angle of the blades.

“Beyond that, the industry has worked with members of the UK’s leading acoustics institute to develop a planning condition for local authorities to use, which we’re publishing today alongside this work. This states that if OAM occurs, it’s up to the wind industry to resolve it.

“The planning condition benefits local communities which host wind farms as well as developers, by reducing the risk of complaints and by allowing operators to tackle noise issues without the need for planning authorities to issue orders restricting turbine operation”.

A spokesman said: “We have had only three complaints about a humming noise this year and all have been in December. Two came from Westbury-on-Trym and one suggests it may be connected to the wind farms.”