### Sound

 Supporting files for this material can be found here.SoundA vibration is one complete back and forth motion of an object.  Some vibrations are able to make sounds - like a guitar string vibrating back and forth.  The rate of vibration is measured in Hertz (Hz).                            1 Hertz = 1 Vibration per SecondSound cannot travel through space - it must go through a medium (a substance that allows sound waves to travel through it).Sound travels in waves through the air (or other medium).  The air particles vibrate, creating compressions (where the particles are squished together) and expansions (where they pull aways from each other).  These compression waves are the sound waves.  For a good visual of this process, click here and look at the "Longitudinal Wave".Wavelength is the distance from the top of one wave to the top of the next wave.Frequency is the number of waves/vibrations that occur in one second.  This is related to wavelength, because shorter wavelengths give higher frequencies.  Frequency determines the pitch (the highness or lowness) of a sound.Amplitude is the height of the wave.  This determines the volume (the loudness) of the sound.  The volume of sound is measured in decibels (dB).   Materials have natural frequencies that they vibrate at.  See the video of the Tacoma Narrows Bridge here.   Video of a sonic boom here. The EarThis list of ear parts goes with the study guide provided in class.  The diagram can also be found on page 392 of your textbook.1. Pinna - Focuses sound into the ear canal.2. Sound Waves3. Ear Canal - Brings sound waves to the ear drum.    You should never stick things into your ear canal (including    fingers or Q-tips), as this can tear the eardrum.4. Ear Drum - Vibrates when sound hits it.5. Malleus (aka: Hammer) - Bone that carries vibrations to the    incus.6. Incus (aka: Anvil) - Bone that carries vibrations to the stapes.7. Stapes (aka: stirrup) - Bone that carries vibrations to the oval    window.    The malleus, incus, and stapes work together to carry    vibrations to the inner ear.8. Oval Window - Lets vibrations into the cochlea (inner ear).9. Semicircular Canals - Help with balance and tell you your    orientation in space.10. Cochlea - Converts vibrations into nerve signals (impulses).11. Auditory Nerve - Brings nerve signals to the brain from the ear.12. Eustachian Tube - Equalizes the air pressure between the      inside and the outside of the ear.13. Ear Drum14. Malleus (Hammer)15. Incus (Anvil)16. Stapes (Stirrup)17. Oval Window18. Watery Fluid - Carries vibrations through the cochlea.19. Round Window - Lets vibrations out of the cochlea.20. Cochlea21. Hair Cells - Create nerve signals (impulses) from vibrations.      Hair Cells are very delicate.  Very loud noises (such as having      your headphones turned up too loud) can injure/kill them.      Since nerve cells do not grow back, this can result in      permanent hearing loss.22. Auditory NerveWeb Resources (Playlist)Hearing & Balance: Crash Course A&P #17  (10:39)Acoustics and Vibration Animations - Animations of different types of waves, including sounds waves coming from different types of sources.The Coolest Things That Sound Waves Do - Video (2:59)What Does Sound Look Like - Video (2:31)Supersonic Flight, Sonic Booms - Video (3:03)The Doppler Effect  (3:02)Vocal Cords - Explanation (2:17) & Singing (3:14)Cochlear Implant - How It Works (2:10) & Simulated Voice and Music (1:57)Supporting files for this material can be found here.
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