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Chapter 10
Physiology of Hearing
Studying auditory physiology can be challenging, as it requires a heavy dose of neurophysiology
at its heart. Following are some activities that might help in your efforts. Some of these are
replicated in the Chapter 9 materials.
Hearing Class Activity 1
Lecture Discussion Questions
1. The term transducer is used a lot in hearing. What is being transduced?
2. Of what use is the pinna?
3. What acoustical benefit is gained from having an external auditory meatus (EAM)?
4. Information from the VIII vestibulocochlear nerve arises from the hair cell. Trace (verbally)
the physical pathway taken by the nerve from an inner hair cell.
5. What are the benefits of the different components of the outer ear to hearing?
6. How were the tuning curves in Figure 10-12 derived and what do they mean?
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cell and its attendant neuron (e.g., that represeting the 1100 Hz portion of the basilar
membrane seen in Figures 10–12 at the bottom right) responds to, for instance, a 110 Hz
signal, a 120 Hz signal, and so on. If your students are audiology savvy, you can even go into
the discussion of how the characteristic frequency is the “best frequency” for hearing and
has the highest sensitivity for that fiber, but that high intensity signals at a much lower
frequency can acvitate it. This gives a partial explanation for why high intensity signals
delivered through hearing aids can’t provide the same discrimination as non-amplified
hearing can, since a given fiber is activated by off-frequency information.)
Hearing Class Activity 2: Calculating the Q10.
This may be a little esoteric for class, but I use it in my graduate auditory physiology course and
the students appreciate it (or simply appreciate an opportunity for me to stop lecturing, as likely).
This activity describes the discrimination ability of the auditory system in terms of the
characteristic frequency and “peakiness” or sharpness of the tuning curve.
The discussion goes something like this. Display the tuning curves in Figures 10–12, focusing on
the bottom two curves. Lead your students into a discussion of which of them is sharper: The
bottom-left or the bottom-right? Now draw their attention to the x-axis scale difference: The
scale on the left terminates around 10,000 Hz, whereas the one on the right is much lower in
frequency.
Hearing Class Activity 3
Decibels
Admittedly, the decibel is not a topic that students appreciate, but successful contact with and
understanding of the decibel is very useful (I call it “touching the beast”). Although this topic is
covered in most hearing science or beginning audiology courses, it never hurts to cover it again.
Hearing Lab 1 is a worksheet designed to bring students into easy, nonpunitive contact with the
decibel. When that is done, an easy step is to calculate the decibel gain from the area ratio and
lever ratio by plugging that into the decibel calculation. Again, it may be too esoteric for your
anatomy and physiology (A&P) class, but the materials are provided within the lab activities
should you want to use them. (Note: This activity was produced as a result of funding by the
Fund for Improvement of Postsecondary Education (FIPSE No. P116B90965-90). It is designed
to be a class activity and is best done in small groups. I have had students really perk up after
succeeding with the decibel.)
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Hearing Class Activity 4
Semicircular Canal Model
One of my colleagues at Idaho State University (Dr. Jeff Brockett) devised an ingenious device
for demonstrating the function of the semicircular canals. He fashioned three polyethylene tubes
(clear) with colored liquid in them, representing each of the three axes of multidimensional
space. He then placed some marbles in the tubes to show the effects of gravity on the fluid. It’s a
great demonstration and worth re-creating.
Hearing Class Activity 5
Available Software
Through a grant from the Fund for Improvement of Postsecondary Education (FIPSE No.
P116A80462), we have developed a software package for instrumentation in audiology that is
available free of charge. The AUDIN self-study program in instrumentation admittedly was
designed with graduate students in audiology in mind, but it has some good basic chapters on
auditory physiology that might be useful in your discussion. If you would like a copy, please
send an e-mail to seikel@isu.edu requesting the AUDIN software, and we’ll get it to you by file
transfer protocol (FTP) server.
Hearing Class Activity 6
Video Tour of the Ear Canal
My colleague at Idaho State University, Jeff Brockett, Ph.D., produced a splendid Moving
Picture Experts Group (MPEG) video tour of the outer ear and tympanic membrane. Please send
me an e-mail at seikel@isu.edu and we’ll get it to you by FTP server.
Hearing Class Activity 7
Auditory Pathway Models
The auditory pathway and auditory reception area of the cerebral cortex have both been
significantly revised as a result of intense study. Consider presenting Figures 10–13 and
discussing the older concepts of the simple pathway as compared with the more complex view of
auditory processing. Also, the revised understanding of Heschl’s gyrus can be pretty exciting in
terms of the “what” and “who” streams of information processed at that level. For instance, the
“who stream” is a constant for all of us primates, in that this is the area that provides information
about species specificity. The beauty of the “what” stream is that in the middle temporal gyrus
the information from temporal and occipital lobes combine, so that the “what” stream for both of
these modalities converges in our favorite lobe.