1. Waves and Sound

2. Objectives for this Unit Identify the frequency, amplitude and phase of a wave. Identify and explain the difference between P and S Waves An object must vibrate to make sound. A vibrating object causes matter around it to vibrate. Sound can move through a solid, a liquid, or a gas. The highness or lowness of sound is called pitch.

3. Waves Definition of wave motion Wave motion is defined as the movement of a material or medium.

4. Types of Waves Transverse (S WAVES) –Up-and-down motion creates transverse waves –Example: Wave at a ball game Compression waves (P WAVES) –Back-and-forth motion creates compression or longitudinal waves. –Example: A Slinky

5. Pictures Transverse Compression

6. Parts of a Wave The Wavelength is the distance between a point on one wave and the same point on the next wave. The wavelength tells you how fast the waves are occurring

7. Parts of a Wave The Amplitude of a wave is the height from the center line to top of the peak. The more energy a wave has the higher the amplitude!

8. Other vocabulary Reflection- is when a wave bounces off a surface it cannot pass through. Refraction- is the bending of a wave when it enters a new medium (substance) at an angle Diffraction- is the bending of a wave as it goes around an obstacle Interference- occurs when two or more waves overlap and combine together

9. SOUND WAVES Why is there a delay when you hear an echo? –It takes time for sound waves to travel from place to place –In dry air the speed of sound is 342 meters/second!

10. SOUND WAVES Sound is carried over compression waves. -Activity- Put your index and middle finger on your throat and say “ahhh” What do you feel? - Those vibrations are actually sound waves!

11. SOUND WAVES VOCAB When I hit these two tuning forks what is the difference between the sounds? The Intensity is the rate at which a waves energy flows through a given area The loudness is the perception of intensity and is subject to a persons interpretation.

12. Common sounds

13. #1 Question: What was the loudest sound ever described by humans? Hint: It was produced by the most famous volcano in recorded history. #2 Question: What was the loudest animal sound ever measured? Hint: It was made by the largest animal on the earth.

14. #1 Answer: In 1883, the Krakatoa volcano in Indonesia erupted and threw ash and stone 300 square miles. The explosive sound from this eruption was heard 3,000 miles away. That's the distance from San Francisco to New York City. #2 Answer: Blue whale communication has been measured up to 188 decibels, making it the loudest recorded sound from a living source. These underwater sounds have been detected 530 miles away.

15. SOUND WAVES VOCAB On your desk are two tuning forks. –Observe the differences between them –Then, lightly hit them on the side of the table What do you feel? What do you hear? What is the difference in the sounds?

16. SOUND WAVES VOCAB You should have noticed the vibrations becoming faster with the shorter fork… the sound waves do not have further to travel so they do not slow down! The frequency of sound waves depends on how fast it vibrates. Pitch- is the frequency of sound as you perceive it. High frequency sound waves have a high pitch and low frequency sound waves have a low pitch.

17. Frequency of sound waves that we can hear!

18. SOUND WAVES VOCAB The Doppler affect- is a change in sound pitch caused by the motion of the sound source