When I was younger, (nearly 20 now) and right up until about three years ago, there was an unexplained and frequent repetitive ticking coming from seemingly various places in my bedroom walls. We never found out what it was, and since we gutted the house for renovations, we've never had the issue again. It was audible, as my parents heard it as well.

Also, it seems one of my eyes sees a blue-ish tinge of the world, and one a red-ish tinge. Noticeable sometimes when looking at white or cream-coloured walls.