Lab 02 - Physics of Sound
Introduction
Now that we know a bit about periodic motion from Lab 01, let us try to apply these principles to
the human body! We have all heard of sound!? Now let’s think of sounds that humans make….
from their vocal cords!
Materials/Supplies
Disposable heavy duty latex cleaning glove, a piece of scratch paper
Time Spent
Approximately 2 hours, does not need to be done at one sitting
Learning Objectives
● Define a sound wave and identify the components in a sound wave equation
● Use the principles of wave characteristics to predict the properties of sound waves in
various situations
How the Larynx Produces Sound
Here is a quick introductory video explaining how the larynx works in the human throat:
https://www.youtube.com/watch?v=b89RSYCaUBo
Beth's First Laryngoscopy - Vocal Cords in Action
And another one showing a live laryngoscopy. Be sure to turn up the sound so you can see
how the larynx works during the sound and no sound:
https://youtu.be/iYpDwhpILkQ
, Please answer the short questions below:
1. What pathway to the larynx does this procedure use?
Answer:
The procedure most likely uses the nasal pathway because the scope appears flexible rather
than fixed, and the patient is able to produce sound during the examination. In this pathway,
the scope passes through the nostril, into the nasal cavity, then through the nasopharynx and
oropharynx, past the epiglottis, and finally into the larynx, where the vocal folds can be
observed.
2. What position do the vocal folds take during normal breathing?
Answer:
During normal breathing, the vocal folds remain relaxed in the open (abducted) position,
allowing air to pass freely through the larynx during both inhalation and exhalation without
producing sound.
3. What happens to the vocal folds during phonation (when the person makes
a vocal sound)?
Answer:
During phonation, the transverse and oblique arytenoid muscles adduct the vocal folds,
causing them to vibrate as air is pushed through them, producing sound. Additional muscles
loosen or stretch the chords to change the pitch.
We will develop a rudimentary understanding of the human vocal system by making some
qualitative observations of our own voices. Make humming sounds with your voice. Try to
change the quality of sound that you produce in as many ways as possible.
4. Describe the ways in which your humming sounds differ from each other.
Answer:
I can change the pitch, volume, and breathiness of my humming. The pitch can be made
higher or lower, the volume can be louder or softer, and the breathiness can be adjusted by
controlling how much air passes through the vocal folds.
5. Open your mouth so you can make an “ahhh” sound. Can you change the loudness of
your sound without changing the “ahhh” sound? How do you do this?
Answer:
Yes, I can change the loudness without changing the “ahhh” sound by pushing more or less
air out from my lungs without changing the mouth position or vocal tract shape. Increasing
airflow makes the sound louder, while decreasing airflow makes it softer.
Introduction
Now that we know a bit about periodic motion from Lab 01, let us try to apply these principles to
the human body! We have all heard of sound!? Now let’s think of sounds that humans make….
from their vocal cords!
Materials/Supplies
Disposable heavy duty latex cleaning glove, a piece of scratch paper
Time Spent
Approximately 2 hours, does not need to be done at one sitting
Learning Objectives
● Define a sound wave and identify the components in a sound wave equation
● Use the principles of wave characteristics to predict the properties of sound waves in
various situations
How the Larynx Produces Sound
Here is a quick introductory video explaining how the larynx works in the human throat:
https://www.youtube.com/watch?v=b89RSYCaUBo
Beth's First Laryngoscopy - Vocal Cords in Action
And another one showing a live laryngoscopy. Be sure to turn up the sound so you can see
how the larynx works during the sound and no sound:
https://youtu.be/iYpDwhpILkQ
, Please answer the short questions below:
1. What pathway to the larynx does this procedure use?
Answer:
The procedure most likely uses the nasal pathway because the scope appears flexible rather
than fixed, and the patient is able to produce sound during the examination. In this pathway,
the scope passes through the nostril, into the nasal cavity, then through the nasopharynx and
oropharynx, past the epiglottis, and finally into the larynx, where the vocal folds can be
observed.
2. What position do the vocal folds take during normal breathing?
Answer:
During normal breathing, the vocal folds remain relaxed in the open (abducted) position,
allowing air to pass freely through the larynx during both inhalation and exhalation without
producing sound.
3. What happens to the vocal folds during phonation (when the person makes
a vocal sound)?
Answer:
During phonation, the transverse and oblique arytenoid muscles adduct the vocal folds,
causing them to vibrate as air is pushed through them, producing sound. Additional muscles
loosen or stretch the chords to change the pitch.
We will develop a rudimentary understanding of the human vocal system by making some
qualitative observations of our own voices. Make humming sounds with your voice. Try to
change the quality of sound that you produce in as many ways as possible.
4. Describe the ways in which your humming sounds differ from each other.
Answer:
I can change the pitch, volume, and breathiness of my humming. The pitch can be made
higher or lower, the volume can be louder or softer, and the breathiness can be adjusted by
controlling how much air passes through the vocal folds.
5. Open your mouth so you can make an “ahhh” sound. Can you change the loudness of
your sound without changing the “ahhh” sound? How do you do this?
Answer:
Yes, I can change the loudness without changing the “ahhh” sound by pushing more or less
air out from my lungs without changing the mouth position or vocal tract shape. Increasing
airflow makes the sound louder, while decreasing airflow makes it softer.
