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Sound

Sound. How Sounds Are Made. What happens when a bell shakes or a drum moves up and down? Vibrations occur – sound is produced when matter vibrates Remember: sound travels as a longitudinal wave. Talking About Sound.

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Sound

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  1. Sound

  2. How Sounds Are Made What happens when a bell shakes or a drum moves up and down? Vibrations occur – sound is produced when matter vibrates Remember: sound travels as a longitudinal wave

  3. Talking About Sound • When you talk, air moves from your lungs over your vocal cords, causing them to vibrate. • As your vocal cords move inward, the air between them is pushed together, creating a compression. • As your vocal cords move outward, less particles of air are left, creating a rarefaction.

  4. Speed of Sound • Speed depends on the medium, NOT the source. • Speed of sound is determined by: 1. Temperature 2. Elasticity 3. Density

  5. Temperature • Lowering the temperature, makes the motion of the particles more sluggish. • The particles have a more difficult time of moving and returning to their original positions. • Sound travels SLOWER at lower temperatures and FASTER at higher temperatures.

  6. Elasticity and Density • Sound waves travel through any medium. • Native Americans use to put their ears to the ground to find out if buffalo were nearby. WHY? • Sound travels about 4 times faster in the ground than in the air. • Sound travels fastest in solids and slowest in gases. • Think about walking in sand: you have to put in a lot of energy to step. Sound is the same. In less-static mediums (like air or water), the waves travel slower. • Solids are usually more elastic. • Would sound travel faster in water or air?

  7. Elasticity and Density (Continued) • Waves travel the FASTEST in solids and the SLOWEST in gases. • GASES LIQUIDS SOLIDS • air water lead • Helium salt water brick milk stone

  8. Properties of Sound • Frequency-number of waves that pass a certain point in a certain amount of time • Frequency is measured in Hertz (Hz). ______________ Hz _________________ Hz

  9. Frequency (continued) • http://www.youtube.com/watch?v=HpovwbPGEoo • http://library.thinkquest.org/19537/java/Beats.html • As the frequency increases, the number of waves increases.

  10. Pitch – a description of a sound as high or low, which depends on the frequency of waves • Sound waves with a high-frequency have a high pitched sound, like a flute • A bass drum has a low frequency, so it produces a low pitch Humans can hear sounds between 20-20,000 Hz.

  11. Doppler Effect http://www.youtube.com/watch?v=Kg9F5pN5tlI http://www.lon-capa.org/~mmp/applist/doppler/d.htm

  12. Doppler Effect (continued) • Doppler Effect – change in sound or light that occurs whenever there is motion between the source and its observer • The pitch of the siren is higher as it approaches you and lower when it moves away from you.

  13. Intensity and Loudness Intensity • Amount of energy carried by a wave in a certain amount of time • The larger the amplitude, the greater the intensity • Intensity is measured in decibels

  14. Interference Constructive Destructive • When sound waves combine to create a greater disturbance • When sound waves combine to make a wave that is less than either wave alone

  15. Applications of Sound Sonar Ultrasonic Cleaning • Sonar: Sound Navigation And Ranging • Bats send out high-frequency sound waves, which bounce off objects and reflect back as echoes. • Bats use echoes to navigate or find their next meal. • Sonar is also used in commercial fishing, in cameras to focus, and in cars to warn of nearby objects. • Ultrasonic waves are used to clean jewelry, electronic components, and delicate machine parts. • Sound waves are sent through the liquid and the vibration knocks off the dirt.

  16. Applications of Sound (continued) Sound and Medicine • Ultrasonic waves are used to diagnose medical problems. • Similar to sonar • Ultrasonic waves may be used to treat medical conditions by destroying unwanted tissue

  17. How You Hear • 1. Sound waves enter the outer ear, which acts as a funnel. • 2. The waves move through the ear canal. • 3. The waves hit a lightly stretched membrane called the eardrum. The eardrum vibrates. • 4. The vibrations hid the middle ear, which consists of three small bones.

  18. How You Hear (continued) • 5.The hammer, anvil, and stirrup send the vibrations along. • 6. The vibrations hit the liquid-filled inner ear. • 7. The vibrations move to the snail-shaped cochlea. • 8. The cochlea has hundreds of nerve fibers which convert the sound into an electrical impulse that is sent to the brain.

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