The Physics Behind A Clarinet
and It’s Reed: It’s More Than
Just Blowing
Molly Risko
Physics 001
Project 2
Background Information- The Clarinet
• Johann Christopher Denner founded the
clarinet in 1690.
• Is a single-reed woodwind musical instrument
that evolved from the first reed instrument, a
chalumeau.
• The difference between the two is two extra
finger holes and a increase in range by two
octaves.
Music Terms to Know
• An octave is a group of eight notes that are within the
interval of two notes. In physics, it has either half or
twice the frequency of vibration as the other.
• A reed is a thin strip of material which vibrates to
create music. A reed functions as an oscillating valve.
• Resonance is the intensification of a sound or tone
produced by vibrations.
• Tones are regular, evenly spaced out waves in the air.
How differently spaced out the waves are effects the
pitch of a note. The more frequent a wave occurs, the
higher the pitch (hence the frequency).
Physics Terms to Know
• Frequency is the number of complete cycles of a
periodic process occur per a period of time.
• As seen with tones, there is spacing between
each waves. The length of this is called the
wavelength.
• Hertz is the unit of measurement to measure
sound. It measures wave peak per second.
• An oscillation, such as what a reed creates, is a
cycle of fluctuation or change between states.
• A sinusoidal wave is a sound wave shaped like a
sine wave.
How It All Comes Together
• Clarinetists need to find the correct reed and pressure to
apply to make terrific sounding music. A springy or flimsy
reed will oscillate on its own creating a squeak…. Not
exactly what the audience wants to hear. The air in the
clarinet and the vibrations caused by the reed both control
each other.
• Sound is produced through an oscillating motion. This is
what the reed functions as. The reed, as well as resonances
in the air create oscillations in flow and pressure. The air in
clarinet begins to vibrate causing sound to erupt out of
open key holes and the bell at the bottom of the
instrument.
• Energy is used by the player to sustain a note as friction is
lost within the clarinet and its walls.
The Reed and Air Flow
• Now, how exactly would a tiny piece of material control air flow and
sound? Look at the chart below. Between the reed and the mouthpiece
there is a tiny space. As seen below, as a player begins to apply pressure,
there is more steady air flow. But as pressure increases the reed bends
slightly, causing the gap between the reed and mouthpiece to decrease.
Eventually the gap will close completely. This leads to air flow of zero.
Pressure and Sound
p represent piano in music or soft sounding. mf represents mezzo- forte, or medium
loud. ff is fortissimo or very loud.
As the waves move away from being sinusoidal, the harmonics become higher. This is
because as we play louder, more pressure is being applied to the reed. The oscillations
then change.
Higher harmonics fall into the frequency sound range that is sensitive for humans, hence
why high notes can be hard on one’s hearing.
Flute vs. Clarinet
• A clarinet is an closed structure, producing a wave length one-quarter the
length of the instrument. The frequency is 140 Hz. All of the pressure is in
the mouth piece and there is zero pressure in the bell (a pressure node)
• A flute is an open structure, that produces a wave length one-half the
length of itself. The frequency is 280 Hz.
• The clarinet is one octave lower than the flute.
Example- Flute vs. Clarinet
• I took a look at an example from the site I grabbed this example off
of. The formula for frequency is equal to speed divided by
wavelength.
• They give that a flute is .6 meters long and a clarinet is .6 meters
also. Since a flute produces a wave half the length of itself, the
wave would be 1.2m because two waves can go through.
• A clarinet produces a wave one-fourth of the length, or four waves.
The wave is 2.4m long.
• So from this information and knowing that sound travels at 340m/s
the frequency of a flute wave is equal to 340m/s/1.2m= 280 Hz and
a clarinets wave frequency is 340m/s/2.4m= 140 Hz.
• The longest wave of an instrument is it’s lowest note. A flutes
lowest note is a C and with a clarinet it is a D# or a middle C. This
proves that a clarinet is exactly one octave lower than a flute.
Harmonics
Harmonics are higher frequencies of played notes that occur from applying
pressure onto the reed. You could also look at harmonics as different pitches.
Because a clarinet is a closed tube instrument, it has mostly only odd
harmonics unlike the flute.
A full wave is the fundamental harmonic but after that the wave can be played
in halves, quarters or thirds, etc.
Sound Production
• Sound is a wave that moves through the air because of variations of
air pressure.
• A clarinet produces sound through these basic steps:
- The air in the instrument is of normal pressure and moves toward
the bell (an opening). There is almost no pressure in the
mouthpiece because of how closed it is. The reed is pulled closer
into the mouthpiece.
-The low pressure moves toward the bell and takes in the normal air
pressure and changes direction and goes through the body of the
clarinet.
-The air is then evened out and the reed returns back to its initial
position. The air from the player meets the moving air in the body
and a high pressure wave escapes from the first open hole.
Reed Types
• As a clarinet player finding the correct hardness, shape and thickness of a
reed depends on each player. Choosing the perfect reed makes all the
difference in one’s pitch while playing.
• Hardness is ranked 1-5, 1 being soft and 5 being hard. Generally, the
harder reeds are better off for clarinetists who tend to bite down. There
are also half step reeds, like 2.5, which are smaller steps in between
hardness.
• Many reeds change shape based on how the player bites down and plays.
Sometimes, the player can shape the reed themselves.
• There are wooden cane reeds and synthetic reeds. Synthetic reeds last
longer than wooden ones, but tend to affect pitch and tone negatively.
Wooden reeds are also adjustable to the players mouth.
• Reed position is very important. When placing the reed on the
mouthpiece you should leave a tip of space from where you place the reed
to the top of the mouthpiece. I will discuss this further in the next couple
of slides.
The Four Rules of A Reed
• My instructor always reminded us to keep our reeds properly placed and
new. I never understood why but after doing some research I realized how
a specific reed can effect pitch, tone and sound.
• Response: a good reed should be able to perform at all dynamic levels
such a p and ff.
• Resistance: how hard you have to blow to produce little or lots of sound. A
reed with low resistance is too easy and takes just as much work to play as
a reed with high resistance. If a reed is either, a player can over blow, and
the tone will not be perfect.
• Tone Quality: is based on the hardness of a reed. If a reed is too soft, the
tone will be dull. If a reed is too hard the sound can be shrill.
• Stability: how the reed performs pitch (flat, stable, sharp, weak). I find this
to be the most important. I feel this is what your audience will recognize if
not perfect. If you cannot maintain a pitch, change your reed.
Reed Positioning
• Always make sure you start off with your reed
center to the mouth piece. If the pitch and
sound are not correct move it ever so slightly
to the left or right. If those don’t work move
the reed down from the tip of the
mouthpiece. Also adjusting the ligature (the
tightening piece) will create a stronger or
lighter sound. This is controlling how much
space a player has to press down on the reed
with to create oscillations from the pressure.
What I have Learned
• Throughout this project I learned how I could
better at playing my clarinet through how much
pressure I apply and how my reed is. Before,
whenever I had a problem with playing I would
always have the conductor fix it for me. But now
that I understand how the reed and clarinet work
together, I can adjust on my own.
• This project was related to the sound wave
section we learned in class. Music is very
interesting to me and I had a better
understanding of it after physics.
WORK CITED
• Jones, Catherine S. "Harmonic Series." Connexions - Sharing
Knowledge and Building Communities. Web. 22 Apr. 2011.
<http://cnx.org/content/m11118/latest/>.
• "Clarinet Acoustics: an Introduction." School of Physics at
UNSW, Sydney, Australia. Web. 22 Apr. 2011.
<http://www.phys.unsw.edu.au/jw/clarinetacoustics.html>.
• "Clarinet." Wikipedia, the Free Encyclopedia. Web. 22 Apr.
2011. <http://en.wikipedia.org/wiki/Clarinet>.
• "Open vs Closed Pipes (Flutes vs Clarinets)." School of
Physics at UNSW, Sydney, Australia. Web. 22 Apr. 2011.
<http://www.phys.unsw.edu.au/jw/flutes.v.clarinets.html>.