Cup your hands behind your ears and the sound changes immediately.

Your outer ear is part of the audio system. Its curves and folds—the pinna—filter sound before it ever reaches the eardrum.

That filtering is not an accident. Sounds arriving from above, behind, or off to one side bounce through the pinna differently. Those tiny changes in timing and frequency response give the brain clues about where a sound came from.

Move the shape and you move the clues.

This is easy to dismiss because ears don’t look much like audio components. No power supply. No capacitors. Not even a reassuring blue light.

And yet they perform a remarkable bit of signal processing before the signal reaches anything we would call hearing.

This also means two people sitting in the same chair do not receive precisely the same sound. Their ears have different shapes, their heads have different dimensions, and their brains have spent a lifetime learning those particular patterns.

The measurements at the chair may be identical.

The listeners are not—and yet they are.

Despite the huge difference in ear shapes among us, our brains have learned to figure it all out and give us the exact mental image of the 3D acoustic space being presented to us.

Remarkable, to say the least.

So, be in awe of the amazing powers we have in those two appendages hanging off the sides of your head.

Dumbo would be proud.