2. Mechanical Waves

3. Mechanical waves Any disturbance made, which travels down a medium
Transverse, and Longitudinal, but only if a medium transfers the energy
No medium, No mechanical wave

4. What is sound?
Sound is
Mechanical and Longitudinal wave that compresses and refracts along an elastic medium
When an object vibrates it causes the air particles around it to move.
These particles bump into particles close to them and this continues until they run out of energy.

5. Try this:
Put your finger on your neck and say “aah” as to yourself with a room voice.
Now say it as soft as you can.
You can not only hear the sound, but you can feel the vibration inside your throat.
What medium carries a sound wave?

6. How does sound travel?
Sound travels through all forms of matter— gases, liquids and solid.
These are called the medium.
Sound Requires a medium
Cannot travel through a vacuum.

7. Pitch: How high or low a sound
Pitch is the frequency of a sound wave
Low pitch = less frequency
High pitch = more frequency

8. How does sound travel?
Sound passes through the medium as longitudinal waves.
When the vibrations are fast you hear a high pitch. When they’re slow, you hear a low pitch.
High Pitch
Low Pitch

9. Sound a longitudinal wave
longitudinal waves compress and rarefract
compress: waves squeeze tightly together (allowing wave to travel)
rarefract: waves seperate apart (released from the squeeze )

11. How else can we change sound?
We can make it louder or softer by changing the amplitude of the height of the wave.
The higher the amplitude, the louder the sound. The lower the amplitude the softer the sound.
Louder
Softer

12. Diffraction —Amount of diffraction depends on the wave length EX
Bending of waves around a barrier or through an opening
—Amount of diffraction depends on the wave length EX
Hearing music playing but not knowing where it’s coming from

13. DOPPLER EFFECT
Apparent change in frequency of a sound wave caused by the motion of the wave and the observer.
Closer to the source = more waves you observe
Farther away = less waves observed