In a video uploaded to YouTube on May 5, 2015, a strange, siren-like noise was recorded over Belfast, Northern Ireland. The “mystery siren” has been reported numerous times in the region, and appears to comes from above, according to those who have reported hearing it.

The sound was recorded most recently by YouTube user Python Guy, who discussed with commenters on his account that an identical sound had been heard in the Newtownabbey area previously. Additional reports out of West Belfast were reported.

“Does anyone have any idea what the sound is or has anyone in the Belfast area heard this?” the uploader asked. “I have also heard thumping and screeching sounds and it always sounds like it is coming from the sky.” It also seems to affect the birds when they are flying, causing them to dip and almost hit the ground when the sound it is at its highest.”

Reports of animal disturbance that accompany strange noises like these appear occasionally in various literature associated with the sounds. Their cause remains unknown, though atmospheric phenomenon is often suggested as their underlying source.

In April, a similar noise which some likened to a mystery siren was reported around Belfast, with one recording of the noise appearing online. Numerous reports of the noise via social media accompanied the sounds, which were compared to air raid sirens. Indeed, the sounds recorded in April appear to most closely resemble an air raid, while the more recent recording of strange “whistling”

Other recent reports of similar mysterious “sky sounds” include vicinities such as Terrace, British Columbia, where noises reminiscent of scraping metal, or as some have said, the calls of an injured animal in the distance, were recorded.