Sound:

Longitudinal Waves

Sound waves make air vibrate . The vibrations in the air make your eardrum

vibrate so you can hear.

For sound to be heard vibrations must have matter to travel through.

You can’t hear sound in outer space because there is no matter/air to carry the vibrations.

*Bell jar video on website: example of sound in a vacuum.

Question: How are astronauts able to talk to each other in space????They communicate through radio waves .

There are 3 states of matter through which sound can travel: solids, liquids, and gases. The speed with which a sound travel depends upon the medium through which it travels.

solid Particles are close together

fastest

liquids Particles are farther apart

Not as fast

gases Particles are very far apart

slowest

Examples: If you put your ear on steel train tracks you can hear the train coming faster than you could hear it through air.Dolphins can communicate more quickly under water than through air.

Loudness/Volume: Volume is loudness or softness. Loud sounds use a lot of energy. Soft sounds use little energy. Example: The harder a drum is hit,

the more an object vibrates. The more an object vibrates the louder the sound it makes.

Wave characteristic that impacts loudness:Loudness= Amplitude/Intensity/Energy

Higher amplitude= Louder Lower amplitude= Softer

Decibels : unit used to measure the intensity or loudness of a sound

Pitch:

Pitch is the highest or lowest sound an object makes.

Objects that vibrate slowly make a low pitch. Ex: drum

Objects that vibrate quickly make a high pitch. Ex: recorder/flute

Wave characteristic that impacts pitch is

Frequency.

The higher the frequency the higher the pitch.

The lower the frequency the lower the pitch.

Low pitch High pitch

Low frequency High frequency

Long wavelength short wavelength

Real world application to music:

Guitar strings

High pitch Low pitchtight looseshort long

Thin thick

Organ Pipes

High pitch Low pitch short long

*Tube demo

Doppler Effect: video on websiteAn increase or decrease in the frequency of sound as the source and observer move toward or away from each other causes a sudden change in pitch like in a passing siren.

Why does this happen?

When a fire truck approaches the pitch sounds higher because the waves arrive more quickly .

When a fire truck moves away you hear a drop in pitch because the waves arrive less frequently .

Higher pitch Lower pitchShorter wavelength Longer wavelengthMore frequent Less frequent

Question: When a source moves toward you is there an increase or decrease in frequency? Explain. Frequency increases

because the wavelengths get closer together.

Review:

Sound is a kind of energy that can be heard.

A sound is made when things vibrate. Amplitude/Volume is how loud or

soft a sound is. Pitch is how high or low a sound is.

TOD: Incorporating reading

Read page 542 – 543 in the text book and complete the following summary statement.

An echo is a sound wave that is ______________________.

You can hear someone talking in a different room through a doorway because sound waves are ___________.