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SOUND WAVES. Sound waves are longitudinal. Sound waves are mechanical- they need a medium and a vibration. Sound does not travel in a vacuum. Sound Waves. VELOCITY OF SOUND. At STP sound travels 3.31 x 10 2 m/s > It’s 4 times faster in water. > It’s 15 times faster in metal.
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SOUND WAVES Sound waves are longitudinal. Sound waves are mechanical- they need a medium and a vibration. Sound does not travel in a vacuum.
VELOCITY OF SOUND At STP sound travels 3.31 x 102m/s > It’s 4 times faster in water. > It’s 15 times faster in metal. Will change due to temperature: v = 331m/s + 0.6(T) (T is in Celsius)
Sound is a range of wave frequencies that the ear is sensitive to. (20Hz- 20,000Hz) Infrasonic sound- Sounds lower than 20Hz Ultrasonic sound- frequencies higher than 20,000Hz Transmission Range- frequencies an organism can produce ( humans 85- 1000Hz)
How does the ear work? • The outer ear “catches the sound waves”. • The middle ear takes the sound waves and “vibrates”the eardrum. • The inner ear sends the messages to the brain. Middle Ear Outer Ear Inner Ear http://www.youtube.com/watch?v=pCCcFDoyBxM
Talking • http://www.youtube.com/watch?v=JzyHKYQzPBk • http://www.youtube.com/watch?v=d-XbjFn3aqE
FREQUENCY High Pitch Frequency- the number of vibrations per second. How the ear identifies this vibration is called pitch. Pitch and frequency are directly proportional. http://www.animations.physics.unsw.edu.au/jw/sound-pitch-loudness-timbre.htm Low Pitch
FUN INFO The phone company uses a combination of frequencies to make a unique sound for each number on the phone. #1 is 687Hz and 1209Hz #2 is 687Hz and 1336Hz #3 is 687Hz and 1477Hz http://soundbible.com/tags-dial.html
AMPLITUDE Amplitude- the maximum displacement of the particles from equilibrium. Amplitude determines the intensity of the sound and how loud it is. http://www.animations.physics.unsw.edu.au/jw/sound-pitch-loudness-timbre.htm
SOUND INTENSITY Sound Intensity- the rate of flow of sound energy from a source. Measured in decibels or watts/meter2 According to OSHA 85dB and higher will produce permanent hearing damage.
HOMEWORK • FROM TEXT BOOK pg 369 #21-23 and #25-30 Show all formula’s and calculations!