Sound Waves Longitudinal Waves either in solids, liquids, or gases Frequency of waves push on ear to make sound
ALL SOUNDS ORGINIATE IN VIBRATIONS!
Sound is much slower than light Sound = 340 m/s, 761.2 mph, 5 second every mile Light = 300,000,000 m/s
Speed of sound depends on temperature of gas , mass of particle, and closeness of molecules
Parts of the Ear
www.lpch.org/.../HealthLibrary/ent/anatomy.html
Current Science Article Safe & Sound By Stephen Fraser
Is loud music having an effect on your hearing?
Did you know that MP3 stood for that?
How may hair cells do you think you have in your ear?
Unit of sound Decibel is the unit of intensity after
Alexander Graham Bell who developed
the telephone
Once you have hit 85 dB, damage begins
Hair cells in your inner ear do not regrow after intense situations!
Humans can hear from a range of 20 to 20,000 Hertz.
Use an oscilloscopeto see sound waves
Sound intensity or loudness depends on amplitude.
Frequency & pitch have a DIRECT relationship.
More waves in a given time, higher pitch
Connection with wavelength Pitch pipes
Wavelength & frequency have INDIRECT relationship
Frequency & pitch have a DIRECT relationship
Sounds & ObjectsNatural Frequency Forced Vibrations Objects vibrate differently
when they are struck. It depends on its elasticity, shape, & medium.
The speed of sound in a material depends on the material's elasticity.
Steel is very elastic (ability to change shape and return back to original shape)
When objects interact together (constructive)
One object is made to vibrate by another vibrating object nearby.
Stringed instruments
Acoustic guitars
What happens when it all adds up together?
Resonance: Objects resonate when there is a force to pull it back to its starting position and enough energy to keep it vibrating. Pushing someone on a swing
Tuning a radio
Tacoma Narrows BridgeIn Washington Stateone windy day
a. The first compression gives the fork a tiny push.
b. The fork bends.
c. The fork returns to its initial position.
d. It keeps moving and overshoots in the opposite direction.
e. When it returns to its initial position, the next compression arrives to
repeat the cycle.
26.8 Resonance