Both ears

Watch the video and listen to the sound.

You use your ears to hear things, and also to tell you where they are. This is called stereophonic hearing.

If you cover one ear up with the palm of your hand (never put fingers, or anything else in your ears!) you will not be able to place things so easily.

With one ear covered, shut your eyes and ask someone to walk around you clapping. Can you tell where they are as easily as when you have both ears uncovered?