We are surrounded day in and day out by a plethora of noises and sounds, some pleasant, some not so much. However, there are some auditory oddities still out there that we just don’t have an adequate explanation for, despite a whole host of theories and hypotheses being put forward for their causes.

From colossal mythical creatures roaming the depths to dangerous secret weapons developed by hostile nations, to (yep, you guessed it) those pesky little green men and even the coming of the apocalypse, the answers to who or what is causing these sounds are just as inexplicable as the sounds themselves.

Here we are going to take a look (and listen) at 5 of these most enigmatic, mysterious and sometimes terrifying sounds that despite our best efforts, they have left us (deaf and) dumbfounded.