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Unit 6: Sound Page 26
I want you to notice two things 3. Feel free to adjust how stretched
here. Sound is vibration. When the the bands are. The more stretched,
bowl is vibrating, it’s making a the higher the note.
sound. When you stop it from
vibrating, it stops making sound. 4. Try plucking a rubber band
Any sound you ever hear, comes softly.
from something that is vibrating. It
may have vibrated once, like a 5. Now pluck it fairly hard. The
balloon popping. Or it may be hard pluck should be louder.
vibrating consistently, like a guitar
string. Again I’d like you to notice
three things here. Just like the
The other thing I want you to last experiment, you should see
notice is that you can actually that the sound is coming from the
see the vibrations. If you put vibration. As long as the rubber
water in the bowl, the tiny waves band vibrates, you hear a sound. If
that are formed when you first hit you stop the rubber band from
the bowl are caused by the vibrating, you will stop the sound.
vibrating sides of the bowl. Those Sound is vibration.
same vibrations are causing the
sound that you hear. The second thing I’d like you to
notice is that the rubber bands
If your mom’s make different pitched sounds. The
worried about thinner the rubber band, or the
making a mess tighter it’s stretched, the faster it
with water vibrates. Another way to say
(and it’s not “vibrating faster” is to say higher
bath night frequency. In sound, the higher the
tonight) then frequency of vibration, the higher
try this the pitch of the note. The lower the
alternate experiment: you’ll need a frequency, the lower the pitch of
mixing bowl, wooden spoon, and the note. The average human ear
rubber bands. can hear sound at as high a
frequency as 20,000 Hz, and as
1. Stretch a few rubber bands low as 20 Hz. Pianos, guitars,
around the box or the bowl. If violins and other instruments have
possible, use different thicknesses strings of various sizes so that they
of rubber bands. can vibrate at different frequencies
and make different pitched sounds.
2. Strum the rubber bands. When you talk or sing, you change
the tension of your vocal cords to
make different pitches.
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