Sound http://www.youtube.com/watch?v=lTetdgpu7MU

http://www.youtube.com/watch?v=8Rl0-SSKVEc http://www.youtube.com/watch?v=lTetdgpu7MU

Sound

• What causes sound?• vibrations of molecules

Sound Waves

• Sound Waves: compressional waves that are produced when vibrations from an object collide with molecules

Sound waves

• Can travel through solids, liquids and gases but not empty space

Speed of SoundDepends on.........

1.  The type of medium (gas, liquid or solid) travels fastest in solids

2. The temperature of the medium- travels through warm mediums faster

How we hear sound…1.  The outer ear gathers sound waves

2.  The middle ear amplifies the sound waves

3.  The inner ear converts the sound waves to nerve impulses

4.  The nerve impulses travel to the brain to be decoded and interpreted

How we hear sound

• Eardrum: a tough membrane in the ear that vibrates when sound enters it

• Cochlea: a spiral-shaped, fluid filled cavity in the inner ear that vibrates and sends nerve impulses to the brain

Properties of Sound • Intensity: the amount of energy that flows through

a certain area in a specific amount of time• High intensity = high energy• Loudness: the human perception of sound intensity

Properties of Sound• Decibel (dB): a unit on the scale of sound intensity• 0 dB is the faintest sound humans can hear• 120 dB main cause pain and damage to ears

Pitch

• Pitch: how high or low a sound is• Frequency and pitch: the higher the frequency the

higher the pitch

Ultrasonic vs. infrasonic waves

• Ultrasonic waves: frequencies above 20,000 Hz

• Infrasonic waves: frequencies below 20 Hz

• Humans: can hear frequencies between 20 and 20,000 Hz

1.  Which 2 animals have the largest hearing range? ______________2.  Which animal can hear the highest frequency sounds? ______3.  What range of hearing does a fish have? __________4.  Which animal has the smallest range of hearing? _______5.  The range of a rodent's hearing is similar to that of a __________

What is the dB of a baby crying?What is the Hz of a baby crying?What is the dB of an airplane?What is the Hz of an airplane?What is the dB of birds?What is the Hz of birds?

Sonic Boom

• http://www.youtube.com/watch?v=-d9A2oq1N38• http://www.youtube.com/watch?v=znlBMHFdCEY

Moving sound • Doppler effect: a change in the pitch of a sound

wave due to the source of the sound moving• Toward: when the object is moving toward the

observer, the pitch is higher• Away: when the object is moving away form the

observer, the pitch is lower

The Doppler Effect

• http://www.youtube.com/watch?v=VYVWhBCwipE• http://www.youtube.com/watch?v=Djz_rtnXSfY

Using Sound

• Sonar: a system that uses the reflection of underwater sound waves to detect objects

• Equation: d = st/2• http://science.howstuffworks.com/391-ultimate-

guide-to-submarines-sonar-video.htm• http://www.youtube.com/watch?v=-fAAxEIFeLU

Using Sound

• Echolocation: animals using sonar to locate prey• http://www.youtube.com/watch?v=gZxLUNHEmPw • http://www.youtube.com/watch?v=ZoNDW0zSRNo• http://www.youtube.com/watch?v=AiBeLoB6CKE

Using Sound

• Ultrasound imaging: uses sound waves to produce images of internal body structures

Music• Music: sounds produced in a deliberate pattern• Instruments produce sound in different frequencies• Natural Frequencies: every material or object has a

natural frequency at which it vibrates• Frequencies of guitar strings depend on thickness, length and

how tightly it's stretched.

Music

• Sound Quality: describes differences among sounds of the same pitch and loudness

• Each instrument has its own unique sound quality

Music • Resonance and music: the sound of music is

amplified by the resonance of instruments

Types of instruments

1. Strings: violin, cello, guitar • Produce notes and the

hollow chamber is the resonator (amplifier)

• Stretching the sting changes the pitch

Types of instruments

2. Brass and woodwinds: flute, trumpet, clarinet•Air is blown through a reed an the air resonates in the chamber (amplifier)•Most are wood but can be brass or other metals

Types of instruments

3. percussion: drums, xylophone, triangle•Resonance happens in a chamber (amplifier)•http://www.youtube.com/watch?v=Of25v8otMJQ&feature=related

Beats

• Beat: occur when sound waves of almost the same frequencies interfere with each other forming a standing wave

• http://www.youtube.com/watch?v=ynqzeIYA7Iw• http://www.youtube.com/watch?v=hip-4KF6z4o• Acoustics: the study of sound• Uses reflection and absorption of sound waves to

design concert halls and auditoriums

1. Sound travels faster in [ warm / cold ] air.

 2.  The bones of the middle ear serve to ______________ the sound.

3.  Sound moves through air by colliding with                                              [ molecules / energy ].   

 4.  Sound moving through air is a                   [ transverse / compressional ] wave.

5. Sound intensity is measured in ____________

6.  Sounds waves with frequencies below 20 Hz are called [ ultrasonic / subsonic ]

7.  Name an organism that uses echolocation: ___________

8. What is the job of the outer ear?

zx9. What is the study of sound called?

10.  Give one example of a percussion instrument.