University of Virginia Physics Department The Energy of Sound A Physical Science Activity

Student Activity

Materials

20 cm of thread	Rubber mallet
Ring stand	Tuning fork
Thumbtack	Cork
Paper	Scissors

Procedure

Follow the directions on the Data Sheet and record observations.

Data Sheet

1. Keeping your mouth tightly closed, hum a long note. Place your hands on the sides of your throat and describe what you feel.   2. Hold your mouth as if you are going to whistle. Again, hum a long note and describe the feeling of your lips.   3. Attach one end of the thread to the ring stand. Using the tack, attach the cork to the other end of the thread. Strike the tuning fork with the mallet and bring it very close to the cork but do not touch the cork. What happens to the cork? 4. Cut a piece of paper 2 ½ inches long and ½ inches wide. Hold the paper between your thumbs and blow on it . Record your observations.   5. From your observations in the last activities, make a general statement about the type of motion that causes sound.

Materials

• Watch that ticks
• Wooden dowel 80-100 cm long
• Metal rod 80-100 cm long
• String (1 meter)
• Metal spoon

Procedure

As you conduct your experiments record your observations in your own words in the table below.

1. Hold a ticking watch as far away from your body as you can. Record whether or not you can hear the ticking in the table.
2. Press one end of the wooden dowels against the back of the watch and the other end against the little flap that is beside your ear. Enter your results in the table.
3. Repeat step #2 using a metal rod instead of the wooden dowel. Record your observations in the table.
4. Tie the handle of the spoon to the center of the meter long string. Hold the string at each end and knock the spoon against the table to make it ring. Listen to the ringing sound for a few seconds then press the ends of the strings against your ears. Observe and record the difference in sound with and without the string pressed against your ear.
5. This time knock the spoon against the table. When you can no longer hear the sound of the ringing spoon, press the ends of the string against your ears. Record whether or not you could hear the ringing of the spoon again.

Data Sheet

Sources of Sound Sound Carrier Description of Sound Watch Air     Watch Wood     Watch Metal     Vibrating Spoon Air     Vibrating Spoon After 5 sec. String     Vibrating Spoon (quiet) String       Questions: 1. Could you hear the watch ticking when you held it at arm's length?   2. Could you hear the watch ticking when you held it against the wooden dowel?   3. Could you hear the watch ticking when you held it against the metal rod?   4. Based on what you heard, which is the best carrier of sound- air, metal, or wood? Which is the second best. 1st _________________________ 2nd ________________________   5. How did the sound of the spoon change when the string was held against your ears?   6. When the ringing of the spoon was too quiet to be heard through the air, could it be heard through the string?   7. Is the string a better carrier of sound than air is?

Materials

• Rubber bands of different thickness
• Ruler
• Three 12 oz soda bottles

Procedure

Follow the directions on the Data Sheet and record observations.

Data Sheet

1. Press a ruler tightly against the desk or table. Allow most of the ruler to hang over the edge. Pull down on the ruler with the other hand, release it and make it vibrate. Listen to the sound made by the vibrating ruler.   2. Slide a little more of the ruler onto the desk or table. Press the ruler on the desk and with your other hand make it vibrate again. Listen to the pitch of the sound. How does it compare to the pitch in number one?   3. Keep sliding a little more of the ruler onto the table or desk to shorten the length of the vibrating portion. Each time you shorten the length record the pitch of the sound in the table. What happens to the pitch of the sound as you shorten the length of the vibrating portion of the ruler?     4. Stretch the rubber band over the length of a textbook and place two wooden dowels or pencils underneath the rubber band at each end of the book. Gently pluck the rubber band and listen for the pitch of the sound.   5. Move the pencils closer together and pluck the rubber band again between the two pencils. Keep moving the pencils closer and plucking the rubber band in between them each time. What happens to the pitch of the rubber band as the pencils get closer together?     6. Place two more rubber bands of different thickness around the pencils and book. Pluck each individually and determine the relationship between the thickness of the rubber band and the pitch. Write your results below.     7. Fill one 12 oz soda bottle 1/3 full with water. Fill a second 12 oz bottle ½ full and a third ¾ full. Tap on each bottle with a pencil and compare the pitch of the sound coming from each one. List the bottles from highest to lowest pitch. Use water levels inside to designate the different bottles. Highest pitch ___________________________________ Middle pitch ___________________________________ Lowest pitch ____________________________________     8. In the bottles of water what is vibrating, making the sound?     9. Use the three 12 oz bottles again, but this time instead of tapping the bottles blow over the tops and try to produce a sound in each one. List the bottles from highest to lowest pitch. Highest pitch _______________________ Medium pitch _______________________ Lowest pitch _______________________   10. What is vibrating to produce the sound, when you blow over the top of the bottle?