Group+4

 -sound waves travel fastest in liquids -slower in liquids -slowest in gases -speed depends on density and elasticity of medium
 * ​** 17.4 Sound and Hearing //​​// (scroll down to the bottom and play the video!)
 * - sound waves are longitudinal waves **
 * -behaviors of sound waves can be explained by their properties: speed, intensity and loudness, and frequency and pitch.**
 * Speed** **:** it takes time for sound to travel from place to place.

-depends on amplitude and distance from sound source -measured in decibels (dB) -for every 10-decibel increase, the sound intensity increases tenfold -depends on individual variable factors **Frequency and Pitch:** -Pitch is the frequency of a sound, as you perceive it -Pitch depends on a waves frequency -Higher and lower frequencies have higher and lower pitches -Pitch depends on your hearing [age could be a factor]
 * Intensity :** rate at which a wave’s energy flows through a given area
 * and Loudness :** physical response to the intensity of sound, modified by physical factors.

-People hear sounds between 20 and 20,000 hertz. -Ultrasounds are sounds higher than most people can hear (over 20,000 hertz). -Ultrasounds are used for sonar and ultrasound imaging. -Sonar is used to graph the ocean floor. -Sonar works by sending out ultrasounds and using the speed of the sound and time it takes to reach the ocean floor. ** The Doppler Effect ** -The Doppler effect is the change in frequency caused by motion of the sound source, motion of the listener, or both. -When a sound source approaches you would hear a higher frequency, as it moves away you would hear a lower frequency. ** Hearing with Ears ** Ears consist of three main regions. The first is the outer ear, the second is the middle ear, and the third is the inner ear. The outer ear gathers and focuses sound into the middle ear, which receives and amplifies the vibrations. The inner ear uses nerve endings to sense vibrations and send signals to the brain. 
 * Ultrasounds **

Most musical instruments vary pitch by changing the frequency of standing waves. Resonance – the response of a standing wave to another wave of the same frequency
 * Music ** [[image:http://i267.photobucket.com/albums/ii290/adair_fan/music-notes.gif]] 

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