2. What is sound?* Sound begins with a vibration. Sounds travel in waves through a medium.

3. What is a wave?* Energy is transferred through a wave. Mechanical waves- travel through a medium Electromagnetic waves- do not need a medium to travel Can you think of examples of each? Which one does this picture represent? Sound waves are mechanical because they need a medium to travel.

4. Mechanical Waves* Transverse Waves The motion of the medium is perpendicular to the motion of the wave Up and Down Waves Longitudinal Waves The motion of the medium is parallel to the motion of the wave Back and Forth Waves **Sound Waves**

5. Another View

6. Longitudinal Waves* Compression When waves are close together Rarefaction When waves are far apart

7. Transverse Waves* Crest- highest point on a wave Amplitude- Volume of a wave (height of a wave) As wave height increases, volume increases Measured in Decibels Trough- lowest point on a wave Frequency- Pitch, high or low (length of a wave) As wavelength increases, pitch decreases Measured in Hertz

8. Amplitude versus Frequency Amplitude Which one will have the higher volume? Frequency Which one will have the higher pitch?

9. What can you hear? Decibels (dB): Volume Normal Speech: 60dB Library: 40dB Close Whisper: 20dB Jet Engine: 140dB Loud Rock Music: 110dB Subway Train: 100dB Busy Street Traffic: 70dB 120dB or above usually causes pain to the ear Hertz (Hz): Pitch Young people can hear frequencies between 20- 20,000 Hz Dogs can hear frequencies that range from 67-45,000 Hz As you age, your ability to hear high frequency sound decreases.

10. Now you will create a diagram for the parts of a wave. Use string and tape. An example is on the next slide.

11. Diagram of a Transverse Wave* CREST TROUGH WAVELENGTH AMPLITUDE

12. Slinky Lab How do waves travel in a spring?

13. Procedure: 1. On a clear tabletop, stretch the spring. Hold one end while your partner holds the other end. DO NOT OVERSTRETCH THE SLINKY!!

14. Procedure 2. Pull a few coils of the spring to one side near one end of the spring. 3. Release the coils and observe the motion of the spring. 4. Describe what happens in words in your ISN.

15. Procedure The arrows below show the direction of the waves. What type of wave have you created?

16. Procedure 5. Have your partner SLOWLY move one end of the spring to the left and then to the right, while keeping the slinky on the tabletop. Be certain that both ends are held tightly. 6. Describe what happens in your ISN. 7. Draw a diagram of what you observed; include arrows to show the direction of the wave. Label the crest, trough, wavelength, & amplitude.

17. Procedure 8. Squeeze together several of the coils, making a compression. 9. Based on #8, draw a diagram of the slinky. Label the compression and the rarefaction. 10. Release the compression section of the spring and observe the energy as it moves down the spring.

18. Conclusions What was the medium for today’s lab? _________________________ What is another word for volume? _____________________________ If these were sound waves, how did you increase the volume in today’s lab? ___________________________________________________ _______________________________________________________ As volume increases, amplitude _________________(increases/decreases). If these were sound waves, how could we have increased the pitch in today’s lab?______________________________________________ _______________________________________________________ As pitch increases, frequency _________________(increases/decreases). If we were measuring the volume of the sound created, what unit of measurement would we use? _________________________________ If we were measuring the pitch of the sound created, what unit of measurement would we use? _________________________________