A scary video has captured the mysterious humming sound which has baffled a city for decades often keeping them awake at night.
Strange: The noise has been keeping residents of this city awake for four decades
For nearly 40 years frustrated people have complained of being kept awake at night by an 'unbearable' low-pitched humming sound.
According to Mirror Online, reports of the so-called Bristol Hum have resurfaced every few years since the 1970s but no-one has been able to explain what causes it.
A variety of different theories have emerged which all have common factors - although strangely, not everyone can hear it. The humming is only audible indoors, it is a low, rumbling noise which is louder at night and is more common in more rural areas.
The debate surrounding the hum has been reignited by a man who recorded it from his attic earlier this month and posted the footage online.
A man Steve Burden, 36, picked up the sound of the wind in a video. A few birds were singing - with a low-pitched humming clearly audible behind them. When he shuts the window the contrasting silence is unnerving.
On the video he says: "I have been hearing some strange noises outside now for a bit. It has been happening over kind of ten minutes.
"I don't know what it is but there has been some strange cloud formations.
"It's freaking me out. I have heard about these noises in other places, but I never thought I would hear it in Bristol. I don't know what it is."
Dad-of-one Steve, lives in Yate, South Gloucestershire - around 12 miles from the centre of Bristol - and runs a flooring company from his loft.
He added: "I had no idea what it was or where it was coming from. There is a construction site nearby and I know there is some work going on there, but it really didn't sound like that."
Listen to the sound in this video below: