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Greg McLain
Professor Steven Errede
December 14, 2015
Physics of Music
History and Physics of Drums
Music has been around almost as long as humans. The use of Instruments by mankind
dates back almost as far as the use of tools, and along with the advancement of the tools, music
has evolved and changed through the ages. People dance to it in social environments, they listen
to it to relieve some stress, and it even can be heard while waiting in the elevator or while
shopping for groceries. Music has become a part of daily life and has an incredibly broad range
of use ranging from spiritual growth to aiding in a simple night of fun.
As music has developed to adapt to its uses and functions, so have its instruments. One
group of instruments that evolved through the ages are percussion instruments. You can hear
drums keeping a beat in most modern music and some types are centered around the drums.
They are one of the oldest instruments to be made and many cultures center religious ceremonies
around their percussion instruments. The instrumental group almost has as deep of a history as
Man.
Drums are a large part of music culture and history, yet most people today don’t know
the history of drums, or how they really work. The reason for this paper is to convey some
history of drums and how the instrument works. I will specifically be talking about
membranophones, or percussion instruments with a membrane that is hit to make a sound (a
drum). A brief history of drum will be discussed, and then some of the physics behind the
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instrument. Hopefully through reading this article, people will further understand not only the
development and physics of drums, but also the development of human beings as a whole.
History
The earliest form of a drum was probably a slit drum. This was pretty much a whole
carved into a log and the log was then hit. Although this type of drum does not have a
membrane, it started the foundations for other ancient drums. Most early drums were made of
simple materials that were readily available to ancient people.
Even though early drums were made of simple materials, the creation and playing of the
instrument was almost magical to ancient people. The sounds from ancient drums were often
considered spiritual and were kept at a high value. In Africa and Asia, the performance and
possession of instruments was considered a gift from the gods and so the instruments were
treated with such regard. In Africa rituals were associated with the drum making process. The
rituals varied from tribe to tribe but every bit of detail and care was put into the creation of these
instruments. In most African communities, the drum maker was a man devoted to the gods. He
was often revered by the community and royalty and was allowed more privileges than others.
When making drums, the creator had to follow the specific rituals which in some situations even
meant following certain dietary constrictions. Even the material the drum was made of was
meticulously chosen as the drum had to be made of a hard wood without blemish and in a few
cases the wood had to even grow in a certain directions. One tribe, the Banyankole of East
Africa, believed that their royal drums were manifestations of the spirits of the gods. The drums
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were brought offerings of milk from sacred cows and were kept in a special house or hut that was
considered holy land. The drums even had a “wife” that took care of them and would spread the
offered milk on them.
Like in African culture, the Samarians had certain rituals for making drums, but while the
Africans focused on the wood of the drum, the Samarians focused more on the head. The bull
had to have a certain pattern and was given offerings before killed and skinned.
Ancient China and Far East Asia also held music at a high value. The culture believed
music was essential to every individuals’ spiritual growth and balance. The earliest Chinese
drum was a two headed instrument filled with rice hulls and was played by temple musicians.
The Chinese drum was also important for military tradition. Rituals were performed on military
drums, giving luck to the soldiers in battles.
While the use of drums in the previously mentioned cultures goes back to ancient times,
Europe’s use of the drum was behind other cultures, and the instrument really didn’t appear
throughout the region until the 12th century. Instruments and percussion instruments were
brought over from other regions, like when people came back from the crusades, but the drum
remained relatively unimportant until it became useful in military communication. The high
volume and ability of drums to convey commands made it a perfect military instrument. Another
drum that became popular during the late Middle Ages was the naker from Arabia. The
instrument was a small pair of kettle drums that was considered an instrument of aristocracy and
was played at royal tournaments and entertainments. Similar to the naker, larger kettle drums
were brought over from Arabia and played mostly for aristocracy. German nobility grew fond of
the drum and eventually it was an instrument of choice. The kettle drum became what we know
as the timpani in modern times. Although the timpani was a favorite of nobility, its inability to
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change pitches quickly made it impractical for most orchestras. The original timpani was
tightened and tuned with several screws that had to be individually tightened or loosened, but
adaptations were made to the instrument to remedy this imperfection. Some innovators created a
hand crank that would uniformly tighten the timpani, thus getting rid of the need for screws,
another created a pedal system that dampened parts of the timpani making the instrument play a
different tune, yet these changes were still not advanced enough to let a timpani be a pivotal part
of the European orchestra. The solution to this problem eventually became to just add more
drums each with a different pitch. Originally two timpani were played at a time, today as many
as 4 or 5 can be part of an orchestra. The advancements in drums eventually led us to the modern
drum set, a very versatile instrument comprised of many drums and percussion instruments. The
use of many drums and cymbals gives us a variety of pitches that we hear in the music today.
Physics
Drums, like all instruments and sounds, create vibrations when hit or disturbed that travel
through the air. The frequency of vibrations creates the pitch that heard and the amplitude creates
the volume. The frequencies and amplitudes depends on the type of drum and what you hit the
drum with. Changes to the drum creates changes to the sound produced. We will go over the
changes and how they affect the sound.
The first factor that affects the sound of the drum is the type of drum played. Generally
speaking there are 3 types of drum: tubular drums, kettle drums, and frame drums. A tubular
drum typically has a cylindrical body with two hole. Either one or both holes are covered by a
membrane and hit. Snare drums and bass drums are examples of tubular drums. A kettle drum is
a drum with one opening, called the mouth, covered with a membrane. The drum’s bottom is
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usually round and an example of this drum would be a timpani. A frame drum is a drum where
the body is small, almost just a hoop, and the membrane is put around the body. These drums are
usually very portable, such as a tambourine. All these types of drums produce different sound
qualities and effect the membrane in different ways.
Although the frame of a drum effects the sound of a drum, the main factor in a drum’s
sound is the drum’s head. The type of material and the tension throughout the head determines
the frequency of vibration of the head and therefore also the pitch of the drum. This can be seen
through the equations given below:
The equations say that velocity of the wave equals the root of the tension throughout the medium
of the wave over the root of the mass per unit length of the medium. The second equation says
that the frequency is determined by the velocity over the wavelength of the wave. Together this
reveals that the frequency is affected by the tension, material, and diameter of a drum head.
The tension of the head is a main component of the frequency and is often the component
that can be changed on a drum by tuning it. People can tighten or loosen the head of a drum
through various means of tuning. When the membrane is pulled tighter, the velocity of the wave
increases, thus increasing the frequency of the wave. This means the tighter the head is, the
higher the pitch. This goes along with loosening the head. When the head is loosened, the drum
sounds lower. Moisture in the air can also affect the tension in the membrane. When most
membranes get dry they shrink, tightening the head, and when they get damp they expand,
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loosening the head. The tension in a drum is the easiest factor to change and is the main way
people tune their drums.
The mass per unit length of a membrane also affects the drum. This refers to the type of
material used to make the membrane. When a drum head is heavier, it produces a lower sound
and when it is lighter it produces a higher sound.
The wavelength of a drum is often the outcome of the size of the drum. When the center
of a drum is hit it usually creates one node or half a wavelength. If the diameter of the head is
bigger, then the node and wavelength are bigger. This causes the frequency to be lower resulting
in a lower sound. This is why a bass drum sounds so much lower than a high tom drum and why
kettle drums that play higher pitches are usually smaller.
The way a drum is hit also affects the sound of the instrument. If you hit a drum hard, it
will make a loud sound. This is a result of the amplitude of the wave created. The harder the
drum is hit, the bigger the amplitude resulting in a higher volume.
The spot where you hit the head is a great influence on the sound of a drum as well. For
example when you hit a snare drum near the edge it is quieter and softer, but when you hit its
center you get the loud clear sound that it is known for. This is a result from the wave formed
when a drum is hit in different places. Different nodes are created, here are a few of them:
The First example is a (0,1) mode and shows the
fundamental vibration for a drum with a circular
membrane. This creates a thump sound that
dissipates quickly which is why if you hit a timpani
at its center it makes a quick thump sound.
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The second example is a (1,1) mode. This
happens when hitting the edge of the drum. This
mode dissipates energy longer over time. This is
why a timpani has its tonal qualities and sound
when you hit its edge.
This is a (0,2) mode and acts much like a (0,1)
mode, it creates the thump sound that you can
hear in bass drums and snare drums.
This is a (2,1) mode and dissipates sound even
longer than a (1,1) mode presenting it with the
sound qualities found when playing on a
timpani’s edge.
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Conclusion
Drums are unique part of human history and science. Tracking the development and
movement of the instrument lets us better understand ancient as well as modern cultures. As
cultures focus more on religion, then the music becomes more religious and ritual like. As a
culture focuses more on individual growth, then music becomes more spiritual introverted. When
a community becomes more social, then so does it’s music, music and the use of drums is a fair
representation of the type of culture a group displays.
As humans advance in science, we can see further physics of music and the drums.
People understand how to create and make new drums and instruments and environments that
best suits the use of the instruments. This will allow individuals to more precisely create sounds
that they imagine and will lead us into continuously altering chapters of music development.
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Bibliography
"Acoustics and Vibration Animations." Mode Shapes of a Circular Membrane. N.p., n.d. Web. 14
Dec. 2015. http://www.acs.psu.edu/drussell/Demos/MembraneCircle/Circle.html
Backus, J. The Acoustical Foundations of Music. N.p.: Norton, 1977. Print
Kunda, Dolores A.. 1979. “Slit Logs and Sacred Cows: The History of the Drum”. Music
Educators Journal 66 (1). Sage Publications, Inc.: 56–65.
http://www.jstor.org.proxy2.library.illinois.edu/stable/3395719.
"Percussion Instruments." Percussion Instruments. N.p., n.d. Web. 14 Dec. 2015.
http://hyperphysics.phy-astr.gsu.edu/hbase/music/percus.html#c1
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