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The Nature of Sound

The Nature of Sound. Objectives. What is sound? What physical properties of a medium affect the speed at which sound travels through it?. What is a Sound Wave?. Sound waves carry energy through a medium without the particles of the medium traveling along.

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The Nature of Sound

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  1. The Nature of Sound

  2. Objectives • What is sound? • What physical properties of a medium affect the speed at which sound travels through it?

  3. What is a Sound Wave? • Sound waves carry energythrough a medium without the particles of the medium traveling along.

  4. What is the mediumthrough which sound waves travel?

  5. What is a Sound? • Sound is a disturbance that travels through a medium as a longitudinal wave.

  6. How are sound waves made? • Air is made up of tiny particles • Vibrations generate a disturbance in the molecules in the air • The force of the disturbance pushes the molecules closer together generating a compression • In between vibrations, the molecules spread out and rarefactions are created.

  7. Sound Waves

  8. Sound Waves

  9. Sound Waves

  10. Pluck a guitar string………. • Plucking the string causes vibrations • The vibrations cause compressions and rarefactions • The sound wave travels through the air in longitudinal wave form

  11. SING! • Vocal cords are like a guitar string • When you speak, air is forced past your lungs and rushes past your voice box • Larynx • 2 folds of tissue vibrate creating sounds

  12. Let’s try it!

  13. How else can sound travel? • Sounds can travel through solids and liquids • Knock • This causes vibrations in the medium • The vibrations generate sound waves

  14. How far can the vibrations travel? • You can put your ear on a train track and hear the train coming from miles away. • Why?

  15. Limitations of Sound: • Sounds can travel only if there is a medium through which to transmit the compressions and rarefactions

  16. Sound in Space • Sounds can not travel through outer space • No molecules in space to compress or rarefy • There is no matter in space

  17. How does sound bend? • Diffraction – sound waves can bend and spread around a corner • Sound waves bend out (diffract) and spread when they hit a barrier or a hole in a barrier

  18. The speed of sound in different media: • The speed of sound depends on the physical properties of the medium it travels through. • Air at room temperature – 342 m/s • The speed sound can travel through a medium depends on: • Elasticity • Density • Temperature

  19. Elasticity – the ability of a material to bounce back after being disturbed • Speed depends on how well the particles in the medium bounce back after being disturbed • The more elastic, the faster sound travels • Examples: • Solids are more elastic than liquids • Gases are not very elastic at all

  20. Density • Density – how much matter, or mass, there is in a given amount of space or volume • The speed of sound depends on how close together the particles of the substance are.

  21. Density Continued • Sound travels more slowly in denser mediums • More dense means more mass per volume • The particles of a dense material do not move as quickly as those of a less dense material

  22. Temperature • Sound travels more slowly at lower temperatures than at higher temperatures • At low temperatures, the particles of a medium are sluggish • Sound waves move and return to their original positions more slowly than they would at high temperatures.

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