Many people have reported hearing the low level humming noise in Horsham town centre, Broadbridge Heath and north Horsham - and now people in Pulborough are also reporting hearing the strange sound.
Some say they have been hearing it ‘for years’ but others have heard it for ‘a few weeks.’
The noise, heard mostly at night, is described as ‘a constant hum, like construction work from far away.’
Some people believe the noise is caused by railway works, kilns at Warnham Brickworks,from sewage works off the A24 or other ‘underground pipes.’
But the source of the sound remains a mystery.
However, the strange noise is a recognised phenomenon world-wide. Up to four per cent of people are said to hear an odd low-pitched sound known as a ‘global hum’ but no source has ever been found.