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Chapter 12, Section 1 The Nature of Sound

Chapter 12, Section 1 The Nature of Sound. Sonic Boom. http://www.youtube.com/watch?v=-d9A2oq1N38. What causes sound? All sounds are created by something that vibrates Energy of these vibrations collides with nearby molecules of air and transfers this energy in all directions from the source

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Chapter 12, Section 1 The Nature of Sound

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  1. Chapter 12, Section 1 The Nature of Sound

  2. Sonic Boom http://www.youtube.com/watch?v=-d9A2oq1N38

  3. What causes sound? • All sounds are created by something that vibrates • Energy of these vibrations collides with nearby molecules of air and transfers this energy in all directions from the source • Sound is a compressional wave A series of compressions and rarefactions move away from the source. The result is a sound wave http://www.brobproductions.com/bigstockphoto_Sound_Waves_1345039.jpg

  4. Moving Through Mediums Sound must have a medium (no sound in outer space!) Sound can travel through any medium (solid, liquid, gas) Speed of sound is determined by a medium’s density: the denser the medium, the faster the speed Why? The molecules in a dense medium are closer and transfer energy more rapidly Air=437 m/s; Water=1498 m/s; Steel=5200 m/s

  5. Moving Through Mediums Careful: the speed of sound DOES NOT depend on loudness (amplitude) Speed of sound is also determined by temperature As temperature increases, the speed of sound increases As temperature increases, molecules move faster 0°C Air=332 m/s; 20°C Air=344 m/s

  6. Human Hearing http://www.infj.ulst.ac.uk/~pnic/HumanEar/Andy%27s%20Stuff/MScProject/workingcode_Local/humanear.jpg

  7. Human Hearing Outer ear: gathers sound waves Middle ear: amplifies (makes louder) sound waves Inner ear: converts sound waves into nerve impulses Brain: decodes and interprets nerve impulses

  8. Outer Ear Outer ear parts: auricle (pinna), ear canal, eardrum (tympanic membrane) Auricle directs sound waves into the ear canal. Ear canal (2-3 cm long) is a passageway to the eardrum. Eardrum (0.1 mm thick) is a tough membrane that vibrates.

  9. Human Hearing http://www.infj.ulst.ac.uk/~pnic/HumanEar/Andy%27s%20Stuff/MScProject/workingcode_Local/humanear.jpg

  10. Middle Ear Middle ear parts: hammer (malleus), anvil (incus), stirrup (stapes), oval window Eardrum vibrations cause the 3 tiny bones (hammer, anvil, stirrup) to vibrate. These bones make a lever system that amplifies the sound wave. The stirrup is connected to the oval window which transfers the vibration to the inner ear.

  11. Human Hearing http://www.infj.ulst.ac.uk/~pnic/HumanEar/Andy%27s%20Stuff/MScProject/workingcode_Local/humanear.jpg

  12. Inner Ear Inner ear parts: cochlea, hair cells Oval window transfers vibrations to the cochlea, a spiral-shaped structure filled with fluid. Within the cochlea’s fluid are tiny hair cells. The hair cells vibrate and stimulate the auditory nerve that sends the information to the brain.

  13. Human Hearing http://www.infj.ulst.ac.uk/~pnic/HumanEar/Andy%27s%20Stuff/MScProject/workingcode_Local/humanear.jpg

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