Pulsating ‘Bass’ Noise over Manchester

Another report of strange sounds comes from Manchester in the UK. These have been coming in since 2011, but, as always, the media has no awareness of their history. We do, however. The video attached, for example, comes from 2012. The poster theorizes that the sounds are from some sort of industrial process, and that’s possible. But they remain of unknown origin. So far, there has been no video or audio posted of the sounds that were heard on September 16, that are referred to in the linked story from the Manchester Guardian.

A question about these sounds: as they appear to have been heard only rarely prior to 2010, and now are heard repeatedly, what has changed?