SoundSoundDo you hear what I hear?

The FactsThe Facts

Sound …Sound …

1. Energy produced & transmitted by 1. Energy produced & transmitted by vibrating mattervibrating matter

2. 2. Travels in waves - longitudinalTravels in waves - longitudinal

3. 3. TravelsTravels more more quickly through quickly through solidssolids than liquids or gases than liquids or gases

Why is Sound Longitudinal?Why is Sound Longitudinal?

Waves in air can’t really be transverse, Waves in air can’t really be transverse, because the atoms/molecules are because the atoms/molecules are not not boundbound to each other to each other fancy way of saying this: gases can’t support fancy way of saying this: gases can’t support

shear loadsshear loadsAir molecules can really only bump into Air molecules can really only bump into

one anotherone another

Imagine people in a crowded train station Imagine people in a crowded train station with hands in pocketswith hands in pocketspushing into crowd would send a wave of pushing into crowd would send a wave of

compression into the crowd compression into the crowd in the direction of in the direction of pushpush (longitudinal) (longitudinal)

jerking people back and forth (sideways, over jerking people back and forth (sideways, over several meters) several meters) would notwould not spread into the spread into the crowdcrowd

but if everyone held hands (bonds), this but if everyone held hands (bonds), this transverse motion transverse motion wouldwould spread into crowd spread into crowd

The EarThe Ear

Sound is carriedSound is carried to our ears to our ears through through vibrating air molecules.vibrating air molecules.

Our ears take in sound waves & turns Our ears take in sound waves & turns them into signals that go to our brains.them into signals that go to our brains.

Middle Ear

VibrationVibration

- Back and forth movement of moleculesBack and forth movement of molecules of matterof matter

- For example,For example,

CompressionCompression- Where Where molecules are being pressed molecules are being pressed

togethertogether as the sound waves move as the sound waves move through matterthrough matter

- For example,For example,- a wave travels through the springs just like a wave travels through the springs just like

sound waves travel through the airsound waves travel through the air- the places where the springs are close the places where the springs are close

together are like compressions in the air.together are like compressions in the air.

Sound WavesSound Waves

ALL sound is carried through matter ALL sound is carried through matter as sound wavesas sound waves

- Sound waves Sound waves move out in ALL move out in ALL directionsdirections from a vibrating object from a vibrating object

Remember Frequency? Remember Frequency?

Frequency is the Frequency is the number of waves number of waves moving past a point in one secondmoving past a point in one second

PitchPitch

A measure of A measure of how high or low a sound ishow high or low a sound is Pitch Pitch depends on the frequencydepends on the frequency of a sound of a sound

wavewave For example,For example,

- Low pitch

- Low frequency

- Longer wavelength

- High pitch

- High frequency

- Shorter wavelength

Sound and InstrumentsSound and Instruments- Instruments can be played at different Instruments can be played at different

pitches by pitches by changing lengths of different changing lengths of different parts.parts.

- For example,For example, - Another way to make different pitches is to Another way to make different pitches is to

change the thickness of the material that change the thickness of the material that vibrates.vibrates.

- For example,For example, A trombone’s mute absorbs some of the

sound waves produced, thus producing a softer

note when played.

SO: SO: ONE WAY TO CHANGE ONE WAY TO CHANGE PITCH IS TO ADD MORE PITCH IS TO ADD MORE

MATTERMATTER (LENGTH, (LENGTH, THICKNESS, ETC.)THICKNESS, ETC.)

This works because there is This works because there is more material so it vibrates more more material so it vibrates more slowly and the wavelengths are slowly and the wavelengths are longer = lower frequency.longer = lower frequency.

Is there another way?Is there another way?

Yes: Yes: Another way to change frequency is Another way to change frequency is to change the space for the vibration. to change the space for the vibration.

EXAMPLE: EXAMPLE: glass bottles with different glass bottles with different amounts of liquidamounts of liquid

The compressions are either pushed close The compressions are either pushed close together (high frequency) or have room to together (high frequency) or have room to stretch out (low frequency).stretch out (low frequency).

Let’s Review!Let’s Review!

You can change You can change PITCHPITCH (high/low notes) by (high/low notes) by changing two things:changing two things:

One = the amount of matter One = the amount of matter Two = the air space Two = the air space What about What about AMPLITUDEAMPLITUDE???? ????

(loudness)???????(loudness)??????? Amplitude changes when force changes the Amplitude changes when force changes the

amount of matter in the compression. amount of matter in the compression. How could you do that? (blow harder, strike How could you do that? (blow harder, strike

harder, etc.)harder, etc.)

Sound Sound Familiar?Familiar?

The Physics of SoundThe Physics of Sound

The Physics of SoundThe Physics of Sound

Healthy CochleaHealthy Cochlea

The cilia ( sensory hairs) appear normal

Damaged CochleaDamaged Cochlea

Loss of cilia as a result of Noise

Hearing Protection Devices Hearing Protection Devices and Their Noise Reduction and Their Noise Reduction

RatingsRatings EAR Foam Plugs (NRR = 29 dB)EAR Foam Plugs (NRR = 29 dB)

EAR CARBOFLEX (NRR= 20 dB)

Moldex PURAFIT Foam Plugs

(NRR=30 dB)

What What ISIS the Speed of Sound? the Speed of Sound?

Carried through air at 345 m/s (770 Carried through air at 345 m/s (770 m.p.h) as m.p.h) as compressionscompressions and and rarefactionsrarefactions in air pressure in air pressure

Example Sound SpeedsExample Sound SpeedsMedium sound speed (m/s)

air (20C) 343

water 1497

gold 3240

brick 3650

wood 3800–4600

glass 5100

steel 5790

aluminum 6420

http://hypertextbook.com/physics/waves/sound/

Stationary Sound WaveStationary Sound Wave

Doppler EffectDoppler Effect

Breaking Sound BarrierBreaking Sound Barrier

SonarSonar- An instrument that uses An instrument that uses reflected reflected

sound wavessound waves to find underwater to find underwater objectsobjects

- For example,For example,

Animals use sonar or echo location to find their prey; these sounds have such a high pitch or frequency that the human ear cannot hear

Humans use sonar to locate or

map objects

Blue Man Group Challenge!Blue Man Group Challenge!

Blue Man GroupBlue Man GroupYou’re HIRED!You’re HIRED!So what am I supposed to do exactly?So what am I supposed to do exactly?

                                                                 

I don’t know what to make… what I don’t know what to make… what do I do!?!do I do!?!

Ugh. That’s tough, isn’t it? I recommend setting Ugh. That’s tough, isn’t it? I recommend setting aside a little bit of brainstorming time first. That aside a little bit of brainstorming time first. That means you let your imagination run wild. Think means you let your imagination run wild. Think of anything and everything that would be cool of anything and everything that would be cool to make, and write it all down. There are no to make, and write it all down. There are no wrong answers in brainstorming. Just go crazy!wrong answers in brainstorming. Just go crazy!

Still stuck? Look around your house and Still stuck? Look around your house and neighborhood. Broken umbrella? Paper bag? neighborhood. Broken umbrella? Paper bag? Floss? Let yourself imagine how those could Floss? Let yourself imagine how those could create music. Then gather some objects and create music. Then gather some objects and start experimenting. Does anything make an start experimenting. Does anything make an interesting sound? Are you inspired yet?interesting sound? Are you inspired yet?

Can I use or make an instrument Can I use or make an instrument that already exists?that already exists?

No way! You could, if you really wanted No way! You could, if you really wanted to…but wouldn’t you rather challenge to…but wouldn’t you rather challenge yourself to invent something never seen yourself to invent something never seen before? C’mon, I know you can do it! before? C’mon, I know you can do it! Besides, building a piano is really Besides, building a piano is really complicated. And putting a piece of string complicated. And putting a piece of string on top of a piano isn’t really on top of a piano isn’t really groundbreaking, either.groundbreaking, either.

Let’s look at some examples!Let’s look at some examples!

InstrumentsInstrumentsAwesomeAwesomeNot AwesomeNot Awesome

Shoe box with rubber bands attached Shoe box with rubber bands attached Oatmeal box with beads in it or paper on top Oatmeal box with beads in it or paper on top to create a drumto create a drum

Tambourines made from paper platesTambourines made from paper platesBongos made from tubs and paperBongos made from tubs and paperEtcEtc

How are you graded?How are you graded?

Lets look at the rubric.Lets look at the rubric.

What are some practical What are some practical ways we use sound ways we use sound

energy?energy?The Human EarThe Human Ear

IntroductionIntroduction

Your ear Your ear converts sound waves into converts sound waves into nerve impulsesnerve impulses that your brain that your brain interprets.interprets.

Parts if the EarParts if the Ear

The Outer EarThe Outer EarContains the pinna, ear canal and ear Contains the pinna, ear canal and ear

drumdrumThe Middle EarThe Middle Ear

Contains three bones: hammer, anvil & Contains three bones: hammer, anvil & stirrupstirrup

The Inner EarThe Inner EarContains the cochlea and auditory nerveContains the cochlea and auditory nerve

How it works – in a nut shellHow it works – in a nut shell

At the outer ear, sound waves are At the outer ear, sound waves are focused by the focused by the pinnapinna down the down the ear ear canalcanal to the to the eardrum.eardrum.

The sound waves make the eardrum The sound waves make the eardrum vibrate.vibrate.

The vibrations are amplified by 3 The vibrations are amplified by 3 middle ear bones, the hammer, anvil middle ear bones, the hammer, anvil and stirrup. and stirrup.

How it worksHow it works

The stirrup transfers the vibrations to The stirrup transfers the vibrations to the the cochleacochlea within the inner ear. within the inner ear.

The vibrations activate The vibrations activate hair cellshair cells inside inside the cochlea, which send electrical the cochlea, which send electrical signals to the brain along the signals to the brain along the auditory auditory nerve.nerve.

The brain interprets these signals as The brain interprets these signals as soundsound

High vs. Low SoundsHigh vs. Low Sounds

High pitchHigh pitch sound carry sound carry more energymore energy and travel and travel furtherfurther into the cochlea into the cochlea

Lower pitchLower pitch sounds carry sounds carry less energyless energy and don’t travel and don’t travel as faras far into the cochlea into the cochlea

Anatomy of the Anatomy of the Human EarHuman Ear

Intensity and LoudnessIntensity and Loudness

The The intensity intensity of a sound wave is the of a sound wave is the amount of energy the wave carries per amount of energy the wave carries per second through a unit area. second through a unit area.

Loudness, or sound level, is measured in Loudness, or sound level, is measured in decibels (dB)decibels (dB)

SoundSound Loudness (dbs)Loudness (dbs) Hearing Hearing DamageDamage

Average HomeAverage Home 40-5040-50

Loud MusicLoud Music 90-10090-100 After long After long exposureexposure

Rock ConcertRock Concert 115-120115-120 ProgressiveProgressive

Jet EngineJet Engine 120-170120-170 PainPain

Space shuttle Space shuttle engineengine

200200 Immediate and Immediate and irreversibleirreversible

FrequencyFrequency

Frequency is measured in Hertz (Hz)Frequency is measured in Hertz (Hz)The frequency of a sound wave is the The frequency of a sound wave is the

number of vibrations that occur per number of vibrations that occur per secondsecondMeaning, a frequency of 50 Hz means Meaning, a frequency of 50 Hz means

fifty vibrations per second. fifty vibrations per second. People hear sounds with frequencies People hear sounds with frequencies

between 20 HZ and 20,000Hz.between 20 HZ and 20,000Hz.

Ultrasound

- sound waves with frequencies above the normal human range of hearing. Infrasound - sounds with frequencies below the normal human range of hearing.