Saturday, August 23, 2014

Digital Human Hearing

Digital electronic technology may have been an unfamiliar term just a few short decades ago in our science classrooms when I began teaching. When my science class members studied the physical qualities of sound, followed by basics of the ear and human hearing, I do not recall digital technology being part of our discussion. Perhaps we were more focused on learning the mechanical transmission of sound through the ear canal, eardrum, the auditory ossicles (small bones from the eardrum to the cochlea), and the cochlea where mechanical transmission of sound ended. We were at the cusp of the Digital Age. Many did not know what the Digital Age meant. It was triggered by the recent phenomenon known as The Digital Revolution which began after mid-20th century.

We now understand more fully the importance of digital technology. Whether or not many of our older citizens appreciate and understand it, digital technology now rules our lives. Virtually all of our communications media runs on discrete digits. We translate “digits” as Information transferred through millions of “on” or “off” signals. Often, information is conveyed as a series of zeroes or ones. On or off signals, or zeroes or ones, assume many different forms. In the human body, electrical impulse information transmitted in billions of neural passageways is also digital. 

After the transmission of sound waves from the outside world enters the snail-shaped cochlea, the auditory signals change from mechanical to electrical. The fluid of the cochlea surrounds multiple regions of hair cells each sensitive to a different frequency of sound. After the tiny hair cells are moved mechanically by compression waves traveling through the cochlear fluid, the sound transmission is transduced. That means the energy form converts from mechanical to electrical. On or off electrical impulse transmission comprises one of many different forms of digital information.

The cochlear hair cells transmit many forms of auditory information in addition to differences in the pitch of sound. For example, the ear distinguishes between loud and soft and also distinguishes directionality of sound sources. In addition, the brain interprets subtleties such as overtones, helping us distinguish among hundreds of different musical instruments. Overtones help us identify the voices of hundreds of acquaintances. A minimal scientific explanation of mechanical to electrical transduction is found in quotes such as “(hair cells)…are at the core of electro-mechanical transduction; the transformation of sound vibration into a neural signal that can be interpreted by the brain.”

Today’s young people are being raised in a digital culture. Digital technology has changed our culture in significant ways. Compared with wonderful advances in analog technology up until the digital revolution arrived full force in the latter half of the 20th century, digital technology is now a cause for jaw-dropping wonder at the onset of the 21st century. The explanation of how digital devices work and how to operate them still bewilders many people over 60 years of age.

My concern with this discussion of human hearing must not rest with stating that sound impulses through auditory neurons are simply “digital.” The real divine genius of the Creator in designing an auditory digital system which codes for communication of bewilderingly complex information in our human brain is a cause for worship. Perhaps we may better grasp what bio-science authors mean when they use the phrase the neural code. Codes are the product of a mind—God’s mind!