The droning noise can be faintly detected in a video posted by Ian McConnell on Twitter, who said the sound lasted for “hours” into the small hours of Saturday 9 November.
Another Twitter user conducted a spectrum analysis of the sound, revealing its peak frequencies.
A quick analysis with my spectrum analyser app gives me these peak frequencies. pic.twitter.com/R7tb7Y3Cd0— Mark Stronge (@markoftec) November 10, 2019
But speculation as to the origins of the noise remains rife, with suggestions ranging from the newly introduced 5G mobile network to a car horn and even ‘the sound of Brexit’.
The Belfast Telegraph has more on the story HERE.