I mean we hear the sound of our blood rushing through the veins of our ears at all times, but our brain filters it out. That the "sound of the ocean" you hear when listening into a conch, it just amplifies the bloodwaves. Other fun stuff our brain does: Our eyes are actually perceiving the world upside down and with a blind spot right in the middle.
The way senses are processed is almost unbelievable.
When your eyesight is partially damaged (by a laser, for example), your brain will fill in the spots, so you won't even realise there's a problem until it's too late (too much damage to cover up).
As the above stated, there's a blind spot (although I don't think it's smack in the middle) - there are tests online you can try to 'see' it.
Your sight also automatically enhances objects it thinks are important, and will predict movementsand patterns, e.g. a baseball you're trying to hit.
There's also no colour in peripheral vision, although the brain does colour it in.