You have two ears so that you can hear which direction sounds are coming from. The brain detects long lines of sound waves or sound patterns that we hear by comparing the information coming from each of our ears. If a dog is barking on the left side of you, the sound will arrive to your left ear a little faster than to your right ear. Also, the sound of the barking will be louder in your left ear than in your right ear. Your brain notes the miniscule difference in time and loudness, and lets you know where the sound is coming from.