This eerie video captures the mysterious humming sound which has baffled a city for decades.
For nearly 40 years frustrated people have complained of being kept awake at night by an ‘unbearable’ low-pitched humming sound. 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.