Ah, yes! Another installment of the famous, home-cooked labs, known as Cellar
Physics. DO ANY TWO, and completely answer corresponding questions on a separate
sheet of paper. (A graded homework assignment.)
Experiment one: The oven surprise!
- Simply take a cold rack out of a cold oven. Be sure that you
do not let this potentially greasy item bump into ANY furniture, etc.
etc.! If you can’t manage this, then get a wire coat hanger (but it won’t
be as good an effect, hee-hee).
- Tie two strong (about 60 cm) strings to it.
- Wrap one string around one index finger and the other string around the
other index finger. Stick those fingers (GENTLY!) into your ears.
- Now get someone to hit the rack with a spoon or other suitable object.
- Try it with other metallic objects hanging from strings
Experiment two: The Old Glass Trick
Get permission to use some wine glasses. (Sometimes these are expensive
items, be careful)
Fill them up with varying levels of water, or if you have just one, do
trials with different amounts of water.
Wet your finger and hold the base of the glass and gently run your finger
around the rim of the glass to get it to vibrate and produce sound.
Try to get the sound louder/softer
Experiment three: Ye olde gramophone
Obtain some old record that you know nobody cares much about
(suggestions: The Osmonds, The Knack, Lawrence Welk’s Greatest Hits)
Put it on a record player, or find a way to get it to spin freely
Obtain a sharp sewing needle and poke it through the end of a paper cone
Experiment with ways to get the needle to contact the spinning record to get
it to produce sound
Experiment with the cone to get it to amplify the sound
- Experiment with the record speed and direction of rotation
Experiment four: Sound effects
Get permission to use a portable tape recorder
Place the microphone so that it is in contact with various objects
that make noise when struck (The sky’s the limit on this one, folks.)
Come up with five sound effects using the microphone in this manner.
(for example: The laser sound in Star Wars was discovered through this type
of random experimentation. Their source: A support cable for a telephone pole)
QUESTIONS: Use your book as a helpful reference. Answer in
- In this experiment what is the medium through which the sound is
- What evidence, or observations did you make that support the idea that this medium
is good at transmitting sound?
- What happens to the sound wave if you grab a string between the rack and
your ear? Where do the sound waves go? Do any waves get through? What would
you do to answer this question in a controlled fashion?
- If you change from one medium to another, which of the following
properties of the wave change? Wavelength, amplitude, speed, frequency.
- Observe the water as you make a sound. Describe what happens. Why?
- What is the relationship between the water level and the pitch?
- When the pitch of a sound wave goes up, what properties of the wave are
changing: Frequency, speed, wavelength, amplitude?
- If you wanted to get a second wine glass to resonate when the first one is
making noise, what would you do to the second glass?
- Look closely, (or with a magnifying glass) at the record. Describe what you
see. How does what you see produce sound?
- Why does the cone amplify the sound. What is it doing to the waves to help
you hear them?
- If sound is being amplified, then what property of the sound waves is being
- Does the record produce sound when spun backwards? Why? Describe your
- Why does the microphone’s contact with the object dramatically change the
sound you hear?
- If the microphone contacts an object, then what is the medium for the sound?
- Through which medium does sound travel best? (Air, Water, Metal) Why?
- Through which medium does sound travel worst? (Air, water, metal) Why?