Sound Frequency
Grade Level: 4
Strand: Understanding Matter and Energy
Topic: Light and Sound
Lesson Expectation: Explain how vibrations cause sound
Required Materials:
- 6 clear glass bottles of equal size
- Water
- Metal spoon or stick
- Optional: Food colouring
Procedure:
1) Arrange empty glass bottles and test by tapping and blowing into the bottles
making note of the fact that they all make the same noise when empty.
2) Fill up glass bottles with water at different levels. (Make sure no two bottles are
filled with the same amount of water)
3) Arrange the bottles in order from least to most water or most to least water.
4) **Optional** Add food colouring to the water in the bottles for effect.
5) Once bottles are filled, use the spoon to hit each bottle.
6) Make note of the sound made by each bottle and reasons as to why there is a
difference in sound made.
7) Now blow into each bottle to produce a sound.
8) Make note of the sound and reasons why you think there is a difference between
hitting the bottle and blowing into it.
Scientific Explanation:
- When you have the bottles filled at different levels and you begin to hit each
bottle, you notice a difference in sound. The bottle with the least amount of
water produces a high-pitched sound and as you continue to add more water to
each bottle and hit them you produce a sound with a lower pitch. The sound is
produced due to the vibrations that occur when you strike the bottle. The bottle
with the least amount of water has more space for the sound waves to move out
of the bottle at a faster pace and faster vibrations create a high sounding pitch.
For the bottles with more water there is less space for the sound waves to move
through the air causing the sound vibrations to move at a slower rate, therefore
creating a lower sounding pitch.
- When you blow into the bottles, you notice the opposite in sound pitches occur.
This is because when you blow into the bottle with the least amount of water, the
sound waves have to travel further down into the bottle then travel back out of
the bottle to create sound. This causes sound waves to travel over a further
distance, thus vibrating at a slower pace to create a lower pitch. When you have
more water in the bottle, there is less space for the sound waves to travel in and
out of the bottle. This means the sound waves vibrate quickly and creates a
higher sounding pitch.
Definitions of Concepts:
- Sound: a vibration or a wave of molecules caused by the motion of an object.
Without motion or vibrations, there can be no sound. When an object moves or
vibrates, the air molecules around the object also vibrate.
- Sound wave: Sound waves vibrate at different “frequencies” as they move
through the air.
- Frequency: Measured in cycles per second, or Hertz. The faster an object
vibrates, the higher the pitch. For example, the higher the frequency, than the
higher the pitch.
- Wavelength: When a wave is created the distance between one compression and
the next compression is called the wavelength. The faster the sound waves pass a
given point, the shorter the wavelength and higher the frequency.
- Compressions: Each molecule moves back and forth only a tiny distance, but it is
enough to cause the air particles to bump into each other. This creates areas
where there are many molecules pushed close together
Other considerations: Extend this experiment into a music lesson dealing with pitch
and sound vibrations.
Sources:
http://www.sciencetech.technomuses.ca/English/schoolzone/Info_Sound.cfm
http://www.thenakedscientists.com/HTML/content/kitchenscience/exp/blowing-onbottles/
Catherall, Ed. Exploring Sound. Wayland Publishers Ltd., England, 1989.
De Pinna, Simon. Sound. Raintree Steck-Vaughn, Austin, Texas, 1998.
Seller, Mick. Sound, Noise & Music. Gloucester Press, New York, 1993.
By: Johnny Hinds & Sean Raposo