Adv Physiol Educ 40: 191–193, 2016;
doi:10.1152/advan.00128.2015.
Illuminations
A model to demonstrate the place theory of hearing
Gnanasenthil Ganesh, Venkata Subramanian Srinivasan, and Sarayu Krishnamurthi
Department of Physiology, K. A. P. Viswanatham Government Medical College, Tiruchirapalli, Tamil Nadu, India
Submitted 28 August 2015; accepted in final form 29 February 2016
Address for reprint requests and other correspondence: G. Ganesh, Dept. of
Physiology, K. A. P. Viswanatham Government Medical College, Tiruchirapalli, Tamil Nadu 620001, India (e-mail: [email protected])
specific frequencies were presented for 1 s (the frequencies that
were used in order were 20-100 Hz in 10-Hz steps, 100-1,000
Hz in 100-Hz steps, and 1,000 –20,000 Hz in 1,000-Hz steps,
respectively). Figure 1 shows the application using a lowfrequency sound. The animation was played again with a
popular song that was chosen by the students. Multiple peaks
were seen at different positions on the membrane (Fig. 2).
To assess the usefulness of the demonstration, anonymous
written feedback was obtained from the students (Table 1).
This study was submitted to the Institutional Review Board and
was exempted from review. One hundred and twenty-five
students completed and returned the feedback questionnaire.
The data collected are expressed as percentages of total students. Ninety-five percent of students opined that the demonstration helped improve the understanding of place theory of
hearing. Ninety percent of students felt that this demonstration
helped them revise the topic. Ninety-seven percent of students
recommended this demonstration for future classes of students,
and 86% of students felt that this demonstration was exciting.
Compilation of the feedback is shown in Table 1. Students
appreciated the demonstration and were in favor of such
demonstrations in the future. They described the demonstration
using terms like “helpful,” “innovative,” and “excellent.” None
of the comments were negative.
Limitations. Student feedback was obtained using a simple,
subjective questionnaire, and the students’ understanding of
the place theory of hearing was not tested either before or after
the demonstration. In future demonstrations, such assessments
may be done, and a five-level Likert scale could be used for
student feedback.
In the demonstration, visualization of the place theory of
hearing was possible but the logarithmic distribution of frequency along the cochlear membrane could not be demonstrated owing to the technical difficulties encountered.
Although the displacements of the basilar membrane were
demonstrated, the physical characteristics of the basilar membrane were not incorporated in the software for the sake of
simplicity of the model.
Conclusions. This demonstration is suitable for classroom
teaching. Students were interested in such demonstrations in
the future, and this is an added tool to enhance the first
MBBS students’ understanding of the place theory of
hearing.
Our model offers many advantages over the existing
animations for classroom teaching. First, the combined
display of a Fourier transform and a three-dimensional
representation of basilar membrane displacement allows
students to visualize the breakdown of the input into its
components and relate it to the frequency-analyzing ability
of the basilar membrane. Our software animation can take a
custom audio file as its input. This feature can be used to
enhance interactions with students, thereby increasing their
attention during a lecture. It also adds variety to a routine
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VON BÉKÉSY ‘S EXPERIMENTS showed the existence of traveling
waves in the basilar membrane and that maximal displacement of the traveling wave was determined by the frequency
of the sound (4). The place theory of hearing equates the
basilar membrane to a frequency analyzer. The model described in this article attempts to enhance a student’s understanding of the place theory of hearing using a software
animation to display a three-dimensional representation of
basilar membrane motion in response to user-defined input
(see the APPENDIX).
Although direct visualization of the vibrations of the
basilar membrane (4) or studying the vibrations on life-sized
micromachined cochlear models (5) or building mechanical
models (4) are ideal, such visualizations require time and
expertise. An animation was considered for a classroom
setting. Existing animations that demonstrate the place theory of hearing are prerecorded videos of the basilar membrane oscillations for a predetermined sound/music. We
thought that students will be excited, and thus engaged, to
hear and see how the basilar membrane oscillated for a song
that they wanted. Hence, a software animation whose input
can be any sound file in WAV format was used. It showed
regions of hair cell excitation that depended on the frequency content of the sound.
Materials required. The following materials are required: a
computer with at least 256 MB of RAM and 80 GB of hard
disk space running either Ubuntu 14.04/Windows XP/Windows 8/Windows 10 with speakers.
Construction of the model. A computer program was written
in the Python programming language. It was designed to mimic
the frequency-analyzing ability of the basilar membrane. An
audio file in WAV format with a sampling frequency of 44,100
Hz was used as input. For every second, audio data was Fourier
transformed to obtain the frequency content. The amplitude at
each frequency was obtained and used for the animation. The
animation consisted of three subwindows (Fig. 1). The top left
subwindow represented the stimulus. The top right subwindow
was the Fourier transform of the stimulus. The bottom subwindow was a three-dimensional representation of basilar membrane vibration. Peak-like deformations were seen along the
basilar membrane, to represent the regions where hair cells
were excited for a particular frequency.
Presentation of the model. This demonstration was done for
first-year medical graduates in a lecture hall. Students had
already attended a lecture on the theories of hearing a week
before.
Initially, students were briefed about the animation. It was
then played with a custom-made audio signal where tones at
Illuminations
192
PLACE THEORY OF HEARING
lecture class and helps to break the monotony of a didactic
lecture. Our software model can also be used by students in
a hands-on manner, which can kindle interest in the minds
of the students. Interactions with students during a lecture
enhance their attention (2), and their attention span increases with their interest (1). Students are interested in
animation-based learning (3). Finally, this model is a simplified version of existing computational models.
APPENDIX: SUPPLEMENTAL MATERIAL
Supplemental Material for this article is available at the Advances
in Physiology Education website.
Fig. 2. Screenshot of the animation when a popular song was played.
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Fig. 1. Screenshot of the animation when a sound at 512 Hz was used.
Illuminations
PLACE THEORY OF HEARING
Table 1. Consolidation of feedback on the demonstration of
the place theory of hearing
Yes, %
No, %
193
ACKNOWLEDGMENTS
The authors thank the class of 2014 first-year medical graduates for
participation in this activity.
Not Sure, %
DISCLOSURES
It helped me improve my understanding
of the place theory of hearing.
It helped me review the topic of the
place theory of hearing.
I shall recommend this demonstration
for forthcoming batches of medical
and paramedical students.
Was it exciting?
Other comments
95.2
0.8
4
89.6
0.8
8.8
97.6
85.6
0
4
2.4
10.4
AUTHOR CONTRIBUTIONS
Author contributions: G.G., V.S.S., and S.K. conception and design of
research; G.G., V.S.S., and S.K. performed experiments; G.G., V.S.S., and
S.K. analyzed data; G.G., V.S.S., and S.K. interpreted results of experiments;
G.G., V.S.S., and S.K. prepared figures; G.G., V.S.S., and S.K. drafted
manuscript; G.G., V.S.S., and S.K. edited and revised manuscript; G.G.,
V.S.S., and S.K. approved final version of manuscript.
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3. Singh S, Singh S, Gautam S. Teaching styles and approaches: medical
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4. Von Békésy G. Experiments in Hearing. New York: McGraw-Hill, 1960.
5. White RD, Grosh K. Microengineered hydromechanical cochlear model.
Proc Natl Acad Sci USA 102: 1296 –1301, 2005.
Advances in Physiology Education • doi:10.1152/advan.00128.2015 • http://advan.physiology.org
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Windows users may download the standalone software program at
https://drive.google.com/file/d/0B-bAmlVdKGz_WnJ3all4U1JpVUE
/view?usp⫽sharing.
The program can be downloaded to any location in the computer.
Double clicking the program will start the program (after a slight
delay).
Linux users may use the source code. The source code is split into
two modules. The modules and a README file are attached separately.
The song titled “Meyyana Inbam” from the Tamil film Easan was
used during the presentation.
No conflicts of interest, financial or otherwise, are declared by the author(s).