Sound Waves

Crests= compressions Troughs= rarefaction

Sound Waves are pressure waves

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

Sound waves’ speed increases as you go through air, water, & solids at different temperatures.

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?

Hair Cells

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.

Range of Hearing

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

Loudness & Pitch OSHA Daily Permissible Noise Level Exposure

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

Beats•Special case of interference with two out of synch waves combine

•Occurs in a pattern, periodic

•Hear louder when constructive waves meet