Notes: Name: __________________________

Stamps: Period: _________

NNOTESOTES WWAVESAVES - S - SOUNDOUND

Directions: Fill in the blanks and boxes in the note panel. After notes are done, part of your homework is to fill in the sides with study questions and write a summary that demonstrates you understand what is important in the notes.

SoundQuestions Main Notes

Wave:

The transfer of ____________ without the transfer of ____________.

Wave Diagram – # of wavelengths in the wave below_____

frequency = how many ____________________ pass per second = how often, or frequent, something occurs

units: hertz (Hz) =

period = time it takes for 1 __________________ to pass by

units:

example:The wave above takes 10 seconds to pass by.What is its period?

What is its frequency?

speed =

units:

Types of Waves

• Mechanical waves require ___________ (a medium) in order to travel

Examples:

• Electromagnetic waves ____________ require a medium. They can travel through empty space.

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Mechanical WavesTransverse Wave: medium vibrates _______________________ the direction the energy moves.

Longitudinal Wave: medium vibrates _______________________ the direction the energy moves.

Classify the following mechanical waves as transverse or longitudinal:

A wave at a ball game Guitar string Flag waving in the wind Sound wave

Shaking a rope Water wave Slinky

Transverse Longitudinal

Reflection

Closed / Fixed end

Open / free end

Electromagnetic Waves

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• All EM waves travel at ______________m/s

• Radio Waves: ________________in the EM spectrum

• Visible light is a tiny section of the EM spectrum

• Visible light is between __________________ and _______________

Summary:

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InterferenceQuestions Main Notes

superposition: when two or more waves _________________

• Waves do not affect each other’s _______________

This is why you can hear lines in a song.

• When superimposed, overall amplitude is the _________ of individual wave amplitudes

This explains why it gets louder when many people talk at once.

Draw each wave pulse before, during and after they meet.

BEFORE

DURING Waves above the rest position are positive Waves below the rest position are _________ Add them up

AFTER Waves pass through each other unaffected

Summary:

Sound – volume and pitchQuestions Main Notes

• Sound is a ________________ wave

• Speed depends on both the _______________ and temperature

• Fastest in _________________ (6000 m/s in steel)

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• Slower in _________________ (1500 m/s in water)

• Slowest in gases

Speed of sound in air

• v = __________m/s at 0° C

at average temp: 20° C, v =

If no temperature is given, assume the temperature is ___________

Example:If you hear lightning strike 3.0 seconds after seeing it, how far away did it strike?

Characterizing SoundSound waves are characterized by:

Pitch – “high” or “low” sounds

• Depends on _________________

• Young healthy human ear has a range of 20 Hz to 20,000 Hz• Human voice: 120 Hz to 20,000 Hz• Baby cry: 2000 Hz to 3000 Hz

Frequency and pitch are important in music

• In music, an ______________is a doubling in f

Volume (loudness)

• Depends on the ______________ of a sound wave

• new unit _______________ (db)

• The decibel is based on human hearing

• 0 decibels is the threshold of ___________• Threshold is the quietist sound you can hear• 140 is the sound of a jet on a runway

• decibel scale is __________________

Continuous dB

Permissible exposure

85 8 hours

88 4 hours

91 2 hours

94 1 hour

97 30 min

100 15 min

103 7.5 min

106 3.75 min (<4 min)

109 1.875 min (<2 min)

112 0.9375 min (~1 min)

115 0.46875 min (~30 sec)

_________________

_________________

_________________

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Sound A

Sound B

Sound C

• So, 60 db 70 db means 10 louder• 60 db 80 db means 100 louder• 0 db to 140 db is 100,000,000,000,000x louder

Analyzing Sound Waves

1. For which sound(s) would youhear the lowest volume?

2. For which sound(s) would youhear the lowest pitch?

3. If you hear Sound B and Sound C what will be the same? What will be different?

Summary:

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Doppler Effect

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Stationary Source

Moving Source – where would you stand to hear a higher pitch?

Doppler Effect occurs if either ____________ or ____________ is moving.

in front is ______________ than

the in back

in front is ______________ than

the in back

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•ƒ’ = frequency the ___________ hears

•ƒ = actual frequency of ___________

•v = speed of sound (___________ )

•vo = speed of ___________

•vs = speed of ___________

Picking SignsEx: On a day when the speed of sound is 350 m/s, a police car with a 2,000 Hz siren and a speed of 35 m/s is chasing a car moving at 50 m/s. What frequency does the driver of the car hear?

What is the source?

What is the observer?

Given:

Time to pick signs!

NumeratorIf observer travels away from source, pitch goes _______

•for pitch to go __________, vo must be __________

If observer travels towards source, pitch goes ________

•for pitch to go __________, vo must be __________

DenominatorIf source travels away from observer, pitch goes _______

•for pitch to go __________, vs must be __________

If source travels toward observer, pitch goes _______

•for pitch to go __________, vs must be __________

Our observer is moving ______________ source ( )

Our source is moving ______________ observer ( )

observer hears a ______________ pitch

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ƒ =

v =

vo =

vs =

Summary:

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When the Source is faster than the SoundMach Speed (pronounced: mock)

• A plane traveling at the speed of sound is traveling at ___________

• NASA space shuttles travel at ________ – that’s 25 times the speed of sound!

Sonic Booms Objects moving faster than sound create shock

waves from the compressed air.

An observer hears this as a ___________ or BOOM!

The boom is caused by multiple overlapping wave crests which ____________ interfere

Which plane is moving faster?

The four figures below represent sound waves emitted by moving source.

1. Which picture(s) represent(s) a source moving at less than the speed of sound?

2. Which picture(s) represent(s) a source moving at the speed of sound?

3. Which picture(s) represent(s) a source moving faster than the speed of sound?

Summary:

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