How You Can Tell Where It Is

When you look at something or hear it make a sound, have you thought about how you can tell where it is? How do you determine its direction and how far away it is? Studies of human sight and hearing tell us that two different systems are involved. One system works for sight, and another for sound.

Hold up a finger at arm’s length from your face. Close one eye and look at the finger and what is beyond your finger. Now switch eyes, and you will see that objects beyond your finger appear to move. When you look at a distant object, the brain receives two signals–one from each eye. Based upon how much the background seems to vary, your brain then computes how far away the object is. That’s how you can tell where it is because your brain combines both images to give you a distance perspective.

To locate a sound’s source, the brain gets a signal from each ear. The two signals arrive at slightly different times depending on the width of the skull and the direction of the sound. We cock our heads to take into account the angular location of the source, and the brain creates an auditory spatial map that pinpoints the sound. Your senses handle sound differently from sight because of the difference in speed of the two signals. Light travels at 186,000 miles (300,000 m) per second and sound travels at 1087 feet (331 m) per second. Your brain combines the object’s sound signals received by both ears, and that is how you can tell where it is.

All of this is amazing enough, but researchers at the Max Planck Institute for Biological Cybernetics in Tubingen, Germany, and Queen’s University in Kingston, Ontario wanted to learn more. By using visual tests on a barn owl while monitoring its brain activity, they found that different nerve cells respond to “specific angular differences.” The barn owl used auditory methods with its vision to give it a three-dimensional map of the area. In that way, the owl has an instant picture of where to fly to get the most unobstructed path to its target. The director of the institute said, “We speculate that the brain uses similar algorithms to solve similar problems” such as matching problems.

We take so much for granted about how our basic senses work. As we have said before, David got a small understanding of this which caused him to say in Psalms 139:14, “I will praise you, God, for I am fearfully and wonderfully made. Marvelous are your works.”
–John N. Clayton © 2018