Chapter 21 Section 1

Describe how vibrations cause sound

Explain how sound is transmitted through a medium

Explain how the human ear works, and identify its parts

Identify ways to protect your hearing

Have you ever heard a sand dune sing??

http://www.pbs.org/wgbh/nova/sciencenow/3204/04-recipe.html

Some croak, squeak, whistle, or boom! Frequencies 500Hz - 2,500Hz

Sound is created by vibrations

A vibration is a complete back-and-forth motion of an object

http://image.tutorvista.com/content/wave-motion-sound/longitudinal-waves-rarefaction.jpeg

A longitudinal wave cause by compressions and vibrations traveling through a medium

Air particles vibrate back-and-forth along the path that the wave travels

Sound waves travel in all directions away from their source

http://www.tpub.com/neets/book10/NTX1-14.GIF

All sound waves require a medium

Sounds waves can travel through air, water, glass, and metal…

In a vacuum, there are no particles to vibrate (no sound)

Your ears change sound waves into electrical signals

Outer ear: collects sound waves (funnels them in)

Middle ear: increases the size of the vibrations

Inner ear: organs change vibrations into electrical energy

Outer ear: Pinna Ear canal

Middle ear: Ear drum Hammer, anvil, stirrup

Inner ear: Cochlea Hair cells, auditory nerve, brain

http://www.uptodate.com/patients/content/images/PEDS/19566/Normal_ear_anatomy.jpg

If a tree falls in the forest and no one is around to hear it fall, does the tree make a sound??

Making a sound vs. detecting a sound…

Tinnitus – due to long term exposure to loud sounds Damage to hair cells or cochlea

(permanent) Ringing in the ears Can affect people of any age Can be prevented

http://www.druckkammerzentrum-traunstein.de/HBO_Dateien_Tinnitus/Tinnitus.jpg

Block out loud sounds with ear plugs

Lower volume used on headphones

Move away from loud sounds

http://1.bp.blogspot.com/_tLoHEV37UR4/Rpe77Z_CdMI/AAAAAAAAAC0/y4sIc8UTxPk/s320/Tinnitus.jpg