Question

There are many reasons why all humans do not perceive sounds similarly in our environment, including adaptation, hearing loss and/or deafness.
For 2A-2D, first determine whether the scenario is an example of sensory adaptation, conduction deafness, sensorineural deafness, and/or central deafness.
Second, for the scenarios that are examples of deafness, explain briefly how the scenario leads to deafness (i.e., how does the scenario alter normal auditory processing). If you have selected sensory adaptation as an answer, explain briefly why the scenario does not fall under the categorization of deafness. Use your own words to briefly explain - simply listing definitions is not sufficient. (2.5 points each for matching, 5 points each for correct justification)
2A. Listening to excessive loud noises everyday over years that causes loss of stereocilia
2B. Hearing construction outside when it first begins, but no longer noticing the sound minutes later
2C. Difficulty understanding speech, but no damage to ears or ability to understand nonverbal sounds
2D. A hole in the tympanic membrane caused by an ear infection

Answer 1

Answer: 2A Sensorineural deafness

              2B Sensory adaptation

              2C Central deafness

              2D Conductive deafness

Explanation: The human ear is divided into 3 parts:

• Outer Ear: auricle, ear canal and tympanic membrane;
• Middle Ear: eardrum, tympanic cavity and ossicles (malleus, incus and stapes);
• Inner Ear: oval window, semicircular ducts (attached to cochlea and nerves), cochlea and auditory tube;

The Sensorineural deafness is a type of deafness caused by a damage in the inner ear, either the cochlea or the auditory nerve. It can happen because of medicine toxicity, exposure to noise along the years etc.

So, from the scenarios above, 2A is consistent with sensorineural deafness  since stereocilia are hair cells of inner ear.

Sensory adaptation is a phenomenom that happens when an individual's sensory receptors is exposed to a stimuli for a prolonged period of time. For example, the situation described in 2B. It is not considered deafness because it is not caused by a damage in any part of the ear.

Central deafness is a very rare case of deafness. The damage in this type of deafness is in the brain and not in any of the 3 parts of the ear. That's why the scenario in 2C is the example of this.

Conductive deafness is the second most common type of ear problem and it occurs in the outer ear. One of the causes is blockage in the ear canal by the ear wax, external bodies, osteomas (bone growth) or otitis (oute ear infection). An example of this type of deafness is scenario 2D.