Wednesday, August 6, 2014

Sound Hearing

Our two-word post title implies two different definitions of sound. The term could apply to a physical phenomenon relating to a type of energy generation initiated by vibrations propagating mechanical pressure waves in gases, liquids, or solids. A different definition comes from the fields of human physiology and psychology: Sound is the perception of such waves by the brain. Confusion of the two meanings of “sound” is the basis of a famous riddle quoted in a recent Geico commercial. “Well, did you know that when a tree falls in a forest and no one’s around it does make a sound?” The answer depends on how we understand the differences between physical, physiological, and psychological definitions of sound. 

Sound hearing” may also connote a third meaning. Used in this manner, “sound” connotes healthy, defect-free, or robust. Sound hearing may be a treasured possession of a healthy young person. When ear infections or injuries occur, or when advancing age takes its toll on the human body, our hearing ability may diminish. Hearing may no longer be described as “sound.”

The physical phenomenon of sound has been present in this solar system since its formation. Physical sound vibrations occur in non-living matter. Our earliest planetary atmosphere, therefore, possessed physical sound, but there was no one present to perceive it. Atmosphere has been a component of Earth environment since planets appeared. Earth’s early atmosphere, very different from the composition of today’s atmosphere, obeyed physical laws and possessed “sound.” Early earth bacteria, the only living things on earth for eons, were not equipped to detect or respond to physical sound. They fulfilled divine purpose as they served to oxygenate the earth’s atmosphere and produce many other mineral resources for the benefit of life forms to appear later.

The physiological and psychological phenomena of sound assumed meaning later when living things were created with organs of hearing. Their hearing mechanisms were able to convert physical vibrations to electrical signals for transmission to the brain. Physical sound occurs in non-living matter. But without a mind to analyze, interpret, and act on its signals, the sound is devoid of any meaning. 

Ultimately, the human brain analyzes and interprets the physical sounds we perceive. We have used three words in our discussion of sound—physical, physiological, and psychological. In a sense the ear is the connecting link between physical sound and its psychological effects. If we study brain physiology, we understand that the physical ear is the center link between physical sound in the outside world and the brain. In a sense, the brain does the hearing. The brain processes the millions of electrical signals from our auditory organ—the ear. That our brains are able to make sense of millions of “action potentials,” electrical impulses arriving through neural circuits via our auditory nerve is the subject of past, present, and future research. In reality we have only begun to understand how the auditory center of the brain accomplishes its work.

Our posts have not begun to deal with how the ear functions as a link between the physical sound around us and the brain which actually hears. We may posit that the ear itself does not hear. Rather, it produces and transports action potentials to the brain. When I taught the subjects of hearing and sight, I sometimes stated, “The brain figures it all out.” That statement served as a cover, not for what we know, but rather, for what we don’t know about how human senses work.

Lessons on sound or sight should first begin with a sense of wonder for the psychological processes of hearing and seeing. “Something special” sets living things apart from non-living entities in our world. In turn, “something special” sets humanity apart from every other species, even the marvelous soulish creatures providing us so much pleasure. Understanding this special quality, even at a level young children may understand, is a starting point for understanding sensory gifts. We begin to acquire a small glimpse of what God meant when he pronounced, “Let us make man in our image” (Genesis 1:26).