Physics of Sound Investigation 3, Part 1

1. Physics of SoundInvestigation 3, Part 1 Sounds through Air and Water

2. Materials • Student sheet no. 13 called Sounds through the Air • Student sheet no. 14 called Sounds through Water • Tone generator with 9-V battery • Megaphone • Paper fasteners • Large plastic bags • Tuning fork • Listening tube • Rubber bands • Wood block • Basin/bucket • Stethoscopes • Alcohol • Cotton balls • Paper towels • Water

3. Preparation for teacher • Sound through Air • Roll tagboard into tubes and secure with paper fasteners at each end, and 2 rubber bands in the middle. • Put listening tube, tuning fork, and wood block in bag. • Sound through Water • Fill 4 basins about 2/3 full of water. • Set 2 stethoscopes near each basin. • Keep a supply of paper towels, alcohol, and cotton balls at station. • Megaphone • Curl the fan shaped piece of tagboard into a cone and fastening with 3 fasteners.

4. Back ground • Wind chimes dance in the breeze, collide, and begin to vibrate. The tinkling sound travels from the chime to your ears through the air. • Male humpback whale calls to a mate by creating vibrations in his respiratory system. His song travels a great distance through the water to a listening female. • A bird watcher hears a wood pecker busy at work high in a cluster of trees. Which tree is the wood pecker in? Bird watcher places his ear to each trunk, until he hears the loud hammering sound traveling down through the wood.

5. Sound Travel • Wind chime, whale, and pecking bird = sound source • Ears = sound receiver • Sound can travel through solids, liquids, and gases as go from a source to a receiver. • Sounds travel faster and seems louder when hear it through a solid or liquid than when we hear them through the air. • At great distances, we can observe that sound travels faster through solids than liquids and slowest through the air.

6. Train • 2 people are on a deserted railroad track. • One person with an ear to the solid metal track. • Another person standing up with an ear to the air. • Both people have stopwatches in their hands. • 1500 meters down the track is another person with a big hammer and a red flag. • The flag and the hammer come down at exactly the same time. • The hammer strikes the track to make a loud noise. • When the 2 people see the flag come down, they start their stopwatches. • When they hear the sound of the hammer hitting the track, they stop the watches. • The person with an ear to the track should hear the sound much sooner than the person with an ear to the air.

7. Background • Most of the time, we are close to sound sources, so we tend to think of sound as an instantaneous phenomenon. • Air is a pretty inefficient medium for transmission of sound energy, and becomes increasingly poor as the temperature drops and the elevation increases. • Colder molecules have less energy to begin with, and air molecules are farther apart at higher elevations. • In space, where heat is negligible and molecule density near zero, sound does not travel.

8. To move from one place to another, sound needs a medium through which to travel. • The medium can be solid like a railroad rail, liquid like water, or gas like air. • If there is no medium, sound cannot travel and so cannot be heard.

9. Misconceptions • Sound will not travel to the ear if the listener does not want to hear the sound. • Transfer of sound traveling from sound source directly to an ear in a continuous straight line. • Sound needs an unobstructed line of sight to get to an ear. If it is blocked, the sound will not be hear, or it will be heard softly.

10. School Bell • When the school bell rings, what is the sound source? • How does the sound get from the bell to your ears? • Do you think it travels through the walls or through the air? • If this room were filled with water, would you still be able to hear the bell? • Can sound travel through water?

11. Overview • Every time we hear something, the sound has to travel from the sound source to our ears. • Sound is invisible. • Today, we will find out if sound travels through water and air.

12. Sound through Air • Remind how to use tuning fork. • Demonstrate how to hold by stem and strike on wood or bottom of shoe with little force. • Demonstrate how to use the listening tube to direct sounds to your ear.

13. Sound through Water • Stethoscope – instrument for listening to sounds in the body. • Demonstrate how to use a stethoscope. • Show how to clean the earpieces with cotton ball and alcohol. • Stethoscope amplifies sounds, so do not strike it hard while listening. • Show how to snap.

14. Student Sheet • Distribute • Read the instructions • 15 minutes at stations • Record observations • Clean up before switch stations • Share observations

17. Tone Generator • Begin with audible volume. • Slowly decrease the volume until only students in front can hear the sound. • We have a problem here. • The volume is very soft. • Is there anything you can do at your seats that will allow you to hear the sound? (megaphone, listening tube, cup hands over ear)

18. Amplify Sound • Make sound louder • Megaphone – funnel shaped device that can amplify sounds at a receiver • How do you think this megaphone works?

19. Ear Function • Outer ear – made of flesh and cartilage • Collects and directs sounds much like a megaphone or a listening tube. • Middle ear – inside ear • Inner ear – inside ear • Nerves carry the sound message to brain

20. Review • Stethoscope – used by doctor to amplify sounds produced inside body • Megaphone – amplify sound at the source or receiver • Outer ear – flap of flesh and cartilage that directs sound vibration to the inner ear • Inner ear – where nerves transmit messages to the brain • Can sound travel through water? (Yes, and it is louder and clearer.) • How can sound be amplified in air? (With tubes and megaphones, which gather and direct sound at either the source or receiver.) • How do ears assist hearing? (Outer ears are designed to receive, focus, and amplify sounds.) • Science story – Moving Along

21. The End!!!