Upcoming SlideShare
×

# Sounds

660 views

Published on

0 Likes
Statistics
Notes
• Full Name
Comment goes here.

Are you sure you want to Yes No
• Be the first to comment

• Be the first to like this

Views
Total views
660
On SlideShare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
32
0
Likes
0
Embeds 0
No embeds

No notes for slide

### Sounds

1. 1. Sound – a longitudinal wave phenomena that consists of successive compressions and rarefactions of the medium through which it travels. All sounds are waves produced by the vibrations of material objects. Sound waves must have a medium in which to travel.
2. 2. What’s wrong with this? Suppose you're watching a science fiction movie and one of the scenes involves a spaceship battle in outer space. Spaceship A launches a successful strike on spaceship B. The scene is presented from the perspective of spaceship A. The occupants of spaceship A view spaceship B blowing up as the result of the successful missile strike. They see the flames of the explosion and shortly thereafter hear the thunderous sound of the explosion. While the scene is definitely exciting, there is a significant fault with it in terms of the physics. What law/concept of physics was violated in the filming of the scene? Explain.
3. 3. because: SOUND TRAVELS THROUGH A MEDIUM The sound produced by the bell cannot be heard since it cannot travel through a vacuum. SOUND IS A MECHANICAL WAVE
4. 4.  The compressions are regions of high air pressure while the rarefactions are regions of low air pressure.  The wavelength is commonly measured as the distance from one compression to the next adjacent compression or the distance from one rarefaction to the next adjacent rarefaction.
5. 5. Correspondence between the longitudinal nature of a sound
6. 6. The speed of sound depends on the type of medium and the temperature of the medium.
7. 7. Waves encountering a surface Will all these rays be reflected back to the person? Can the blue person hear the echo? Reflection
8. 8. Specular Reflection
9. 9. Diffuse Reflection
10. 10. How can the two people hear each other? Each of the rays traveled different lengths of way Each of the rays used a different amount of time
11. 11. Variable speed of soundCool air = low speed Warm air = high speed Wave front Plane waves at constant speed Rays are bent away From surface! Refraction Wave fronts if the air is warmer at the ground
12. 12. Variable speed of sound Cool air = low speed Warm air = high speed inversion Rays are bent toward surface! Wave fronts if the air is cooler at the ground Refraction
13. 13. Variable speed of sound wind sound Resulting motion of sound waves Resulting motion of sound waves sound wind The rays are bent upward upwind of the source. The rays are bent downward downwind of the source. Refraction
14. 14. Reflection and refraction  Reflection:  At solid obstacles, a sharp change of direction  Echo, ringing effect in halls  Refraction:  Inhomogeneous speed, gradual change of direction  Air layers with different temperatures, wind Reflection is of more importance to us than refraction.
15. 15. Why can we hear around a corner? Reflection ?
16. 16. Sound waves at obstaclesTop view: Diffraction
17. 17. Diffraction at small openingSmall: d<<λ Wavelength large compared to opening Shadow zone Shadow zone Diffraction bends the wave fronts heavily at the edges of a small Obstacle.
18. 18. Diffraction at large openingSmall: d>>λ Wavelength small compared to opening Shadow zone Shadow zone Diffraction bends the wave fronts only lightly at the edges of a large obstacle.
19. 19. The time it takes for sounds to reach you does not depend on how loud or high the sound is. The speed of sound depends only on the medium through which the sound is traveling Medium Speed m/s) Air 343 Helium 1,005 Water 1,482 Sea Water 1,522 Wood (oak) 3,850 Glass 4,540 Steel 5,200 Speed of Sound in Different Media at 20 degrees Celsius
20. 20. Try to solve: Speed at 20ͦ C Speed at 0ͦ C Speed at 33ͦ C Air 343 m/s Water 1482 m/s Glass 4540 m/s
21. 21. SOUND IS… In the physical sense, 1. The source of sound 3. An ear to receive the sound. the disturbance in matter which are above, below and within the range of human hearing. there are three requirements for sound. They are… 2. Medium for transmitting sound In the physiological sense,
22. 22. Group Activity:  Each group will be asked to design a roof of an outer pavilion (performance stage).. Apply the concept of properties of sound. How will you design? Draw the side view only, and explain in class
23. 23. Speed at 20ͦ C Speed at 0ͦ C Speed at 33ͦ C Air 344 m/s 331 351 Water 1482 m/s 1470 1490 Glass 4540 m/s 4528 4548