1. Sound Science: DO YOU HEAR WHAT I HEAR?
What is sound? How does it relate to music?
From a scientist’s point of view, if a tree falls in the woods, it most certainly makes a sound because it causes vibrations in the air!

2. Sound is a wave. Waves carry energy through a medium.
The medium is what the wave is moving through.
For sound, the medium is usually air, but sound
also travels through solids such as steel and
liquids such as water.
For a simple example, think of this: If you move a jump rope, the wave travels through the rope. The wave moves. The medium is the jump rope. If you understand this idea, you can begin to understand how a string, when vibrated, such as in a guitar, generates or makes sound.

3. Sound is vibrations. When a stringed instrument is
plucked, the string moves up and
down in opposite directions from
Its rest position, causing vibrations
In the string.
The actual motion of the vibration,
like the plucked string of an ‘ud,
is called simple harmonic motion.
When a guitar string is plucked, the string moves up and down in opposite directions from its rest position, causing vibrations in the string. Click on the sound button to hear a recording of the ’ud.
‘Ud (plucked lute) from Syria

4. Waves
Vibration results in waves: water waves, light waves, sound waves, etc. Sound waves (longitudinal waves), like all waves, Have four basic properties: Amplitude Wavelength Frequency Speed
Background For Teachers: Sound is a form of energy when vibrations (rapid back and forth movements) travel through a medium. Three things are necessary for the creation of sound: (1) a source of energy or disturbance, (2) vibrations, and (3) a medium for the vibrations to travel through. The source of energy could be plucking the string of a guitar, blowing across a reed, or hitting a drum. This disturbance causes the string, the reed, or the drumhead to vibrate rapidly. When the drum is hit, the drumhead vibrates and creates a disturbance of the molecules in the air near it. When the drumhead moves to the right, it pushes the air molecules into each other, causing them to become compressed (like a slinky). When it vibrates to the left, the molecules of air move farther apart, creating a rarefaction (the particles are farther apart). These vibrations travel through the air, one particle bumping into another like dominoes, until they reach the ear. Sound, unlike heat and light, cannot travel through space because space has no medium for it to travel through.
Sound waves (longitudinal waves), like all waves, have four basic properties: amplitude, wavelength, frequency, and speed. Amplitude in a longitudinal wave is a measure of how compressed or rarified the medium becomes. High-energy vibrations (hitting the drum harder) cause the molecules to become more compressed. The greater the amplitude of the wave (intensity), the louder the sound is. Frequency is the number of complete waves (vibrations) that pass a given point in a certain amount of time, or how fast the medium is vibrating. The pitch (highness or lowness of a sound) that is heard depends on the frequency of the sound wave. Sound waves of high frequency have a high pitch, while sound waves of low frequency have a low pitch. The frequency of a vibration of a drumhead depends on the material used, the size of the drumhead, and how tightly it is stretched. A tighter or smaller drumhead would create a higher pitch than a looser or larger drumhead. A guitar string that is tighter, thinner, or shorter will have a higher pitch than one that is looser, thicker, or longer. Therefore, size makes a difference in sound. If the shape and material used in two instruments are the same, then the larger instrument will vibrate with a lower frequency and create a lower pitch than the smaller instrument.

5. Sound is a longitudinal wave.
Longitudinal waves are
Pressure waves.
As the tuning fork vibrates,
air gets pushed closer
together, then spreads
farther apart. This makes
areas of high and low
pressure as the waves travel
from the tuning fork.
The tuning fork is made of metal. The waves travel through air.

6. Sound Waves
The same idea works with bells, gongs, chimes, triangles, etc.
Think about the common elements in bells, gongs, chimes, and triangles. How are they held? What creates the sound? Have you ever touched a bell that was sounding? What happens to the sound wave when you touch a ringing chime?

7. Idiophones
These instruments are classified as idiophones, instruments in which the material of the instrument itself, typically when struck, is what vibrates.
Can you see the variety of materials used to construct these instruments? How many can you name?
Bala (gourd-resonated xylophone) from Guinea
Music box from USA

8. More Idiophones Saron (metallophone) from Indonesia
Triangle from Belgium
These idiophones are found in different galleries at MIM. Can you identify them? What are the similarities among these instruments? What are their differences?
Kono (slit drum) from Sierra Leone

9. Even More Idiophones
You will find these instruments at MIM. Upstairs in the Asia gallery, as well as throughout other galleries, there are many idiophones. The gong on the right is found downstairs in the Experience Gallery. You will have a chance to hear it played at MIM. What type of sound do you think it makes? Is it a high pitch or a low pitch? Do you know why?
Gong from Thailand
Gongs from Indonesia

10. Chordophones
Morin khuur (bowed spike lute) from Mongolia.
What do you see that vibrates on each of these instruments?
These stringed instruments are found at MIM. How do the strings generate sound in each case? Do you notice the Mongolian horse-head fiddle, called the morin khuur, on the right?
Keyed zithers from USA

11. Chordophones Strings do the vibrating in chordophones.
What is the generator of sound? With a chordophone, it is the vibrating stretched string. What is the difference between these two stringed instruments? How might the sound differ as a result of their construction?
Nyckelharpa (keyed fiddle) from Sweden
‘Ud (plucked lute) from Egypt

12. Membranophones
In a membranophone, the vibration is from a stretched skin.
What generates sound in a membranophone? It is the vibration of a stretched skin or membrane. If you look closely, you will see this membranophone also has rattles on the side. So, there are two generators of sound in this instrument.
Pandero (single-headed frame drum) from Chile

13. Membranophones
Here are some membranophones you will see in MIM’s Experience Gallery. What similarities do you notice about the instruments? What are the differences? How do you think those will affect the sound?
Talking drums (double-headed hourglass drums) from Nigeria
Taiko (double-headed barrel drum) from USA

14. Aerophones
In aerophones, it’s a column of air that vibrates―hard to see, but it sounds great!
Rondador (raft flutes) from Ecuador
In aerophones, the generator of sound is the vibration of a column of air. You will see aerophones made from various materials at MIM.
Over-the-shoulder horns (valved horns) from USA

15. Aerophones Kudu horns (side-blown trumpets) from South Africa
All of these instruments are aerophones. Which would you say are made of natural materials? Which are constructed of man-made materials? Have you seen instruments like these before? What generates the sound in each of these instruments?
Feadóg stain (duct flute) from the UK
Musical jug from USA

16. Aerophones
There are several ways to start the column of air vibrating. Lips of the player (as in a clarín or trumpet) Reed (saxophone or bagpipe) Turbulence as air flows across the opening (sikus or organ pipe)
In summary, with an aerophone, the generator of sound is the vibration of a column of air. There are several ways to start the column of air vibrating. Can you think of sound makers that you have crafted that use the same principle?

17. Corpophones
When a vibration or action is produced by a body part (or parts), it sends off waves creating sound.
Hand Claps
Finger Snaps
Leg Slaps
A corpophone is defined as a “body sounder” in which a vibration or action is produced by a body part (or parts), sending off sound waves. This category includes handclaps, slaps of the body, snaps of the fingers, and so forth, but does not include vocalizations. Examples of corpophones at MIM include the rhythmic hand clapping and foot stomping as seen in the flamenco dance (Spain).
Foot Stomps
Mouth Clicks

18. What do you know?
Sound is a wave. In a musical instrument, generate sound. With , the sound generator is a vibrating stretched string. Sound travels differently through various , such as through air, solids, and water.
ANSWERS:
Sound is a pressure wave. In a musical instrument, vibrations generate sound. With chordophones, the sound generator is a vibrating stretched string. Sound travels differently through various mediums, such as through air, solids, and water.

19. Want to know more?
MIM has a large collection of musical instruments. Some Use electricity to generate or amplify sound. In other lessons, you will learn about sound generation with a group of instruments we classify as electrophones.
QUESTION: The photo in the slide shows an electric guitar. If you pluck the strings of the guitar while unplugged from the amplifier, what is the sound? What does electricity have to do with sound? The electric guitar and other electronified instruments are classified as electrophones. You will see many instruments like these at MIM. Other lessons will tell you more about the effects of technological innovations, including the use of electricity and sound production, on the development of both the world of musical instruments and performance.
Electric guitar from Taiwan