Science 8th grade
UNIT 11: Sound 11.1 Changing sounds
Science 8th grade
UNIT 11: Sound 11.1 Changing sounds
It's easy to make a sound. Hit a box with a stick Blow into a tube. Pluck a rubber band.
We can make sounds with our vocal cords. Try placing your thumb and fingers gently on your throat while you are talking or singing. You should be able to feel vibrations.
All sounds come from sources which vibrate (move back and forth). You may be able to see the vibrations of a guitar string. You can't see the air inside a saxophone vibrating.
The guitar strings vibrate when you pluck them
Loudness and pitch
There are three types of musical instruments:
stringed instruments (with strings that vibrate), wind instruments (ones that you blow into), and percussion instruments (that you strike).
Musicians learn to make different sounds with their instruments. There are two things they can change:
• They can make the sound of their instrument louder or softer. They can control its loudness.
• They can make the note higher or lower.
They can change its pitch.
Question
1) Loudness and pitch are two important properties of a musical sound.
a: If a musician plays a softer note, which property has been changed, loudness or pitch?
b: If the musician makes the note lower, which property has been changed, loudness or pitch?
Activity 11.1 (Loud and soft, high and low)
In this activity, you are going to look at some musical instruments and consider how the sounds they produce can be changed. If you play a musical instrument, you may be able to contribute more to this activity.
Watch different instruments being played. Suggest how the note can be made louder, and how its pitch can be made higher. Test your ideas.
Show your findings in a table.
Loudspeakers
Loudspeakers are used to produce sounds from computers, radios and television sets.
Inside a loudspeaker is a paper cone. This cone vibrates back and forth to make the sounds that we hear.
In the photograph, some small plastic balls are bouncing up and down on the cone as it makes a sound.
The cone vibrates up and down more when it produces a louder sound. It vibrates up and down more frequently when the pitch of the note is higher. ("More frequently' means more times each second.)
Question
2) Imagine that a loudspeaker is producing a quiet note with a low pitch.
How will its vibrations change:
a: if the pitch of the note becomes higher?
b: if the note becomes louder?