pg. 24

•9/26/13

IQ: What are all of the sounds that you hear in a minute’s time? Write down as many as you can.

What is SOUND? Pg 25Sound is a form of energy that travels in waves.

Sound Waves

•Sound vibrations occur in waves that go out in every direction •Repeated patterns of molecules spreading apart and squeezing together. •ALL sound is carried through matter

(medium) as sound waves

How does Sound Travel?

When energy causes something to vibrate, molecules in the air crowd together, then spread apart, causing sound waves to travel away from the vibrating object

What makes Sound?

•Vibrations: back and forth motion of particles in matter•No medium=no sound because no vibration occurs

OQ. Pg 24

•What is sound and how is it created?

IQ: 9/30/13 pg 26

•Which unit is used to express loudness of a sound wave?

Frequency• Frequency: How many waves go past a point in a second

• Measured in Hertz

Than hereLower Frequency

PITCH and FREQUENCY pg 27• PITCH: measure of how high or low a sound is perceived

to be, depending on the frequency of the sound wave.

• A high frequency is a high pitch. Ex. Chihuahua

• A low frequency is a low pitch. Ex. German Shepherd

LOUDNESS and AMPLITUDE• Amplitude is how tall the wave is from rest position

• Wave amplitude is related to loudness (loud or soft).

• A low amplitude wave has a soft sound.

• A high amplitude wave has a loud sound.

Amplitude

Amplitude

Decibel

• Unit used to express how a loud or soft a sound is perceived

Doppler Effect• Observed change in frequency and pitch of a sound. • Due to the motion of either the sound source or the observer

is moving.• Ex. Police siren, train, motorcycle going past you

•OQ: Which two sound properties are responsible for pitch and loudness of sound? Explain why.

Pg 28

• IQ 10/2/13•Which medium does sound travel through the fastest?

Speed of Sound in Types of Media

•Gas: (air) travels slowest in gas•Speed of Sound in air 344 m/s•Liquids: Sound travels faster in liquids than gas, but slower than in a solid•Solids: Travels fastest through solids •Sound cannot travel through a vacuum (a space that is “empty” of matter).•(Solid) (Liquid) (Gas)

REFLECTIONSound Waves have 3 common features:

•Bouncing back of a wave after hitting a barrier

•Reflected sound waves are called echoes

•Reflects best off of a smooth, hard surface(give examples of where you hear a reflection best)

•Ex. Mirror

•Echo

1. They: a. Have a set wavelength b. Vibrate at different speeds--Frequency: the number of complete wavelengths, or times an object

vibrates per second.c. Carry Energy--amplitude is the amount of energy a wave has--high amplitude sound is made by objects with great vibrating

motion

Echolocation• Use of reflected sound waves to find objects

• Animals use echolocation to hunt food/find objects in their path; these sounds have such a high pitch or frequency that the human ear cannot hear

• Based on how long it takes sound waves to echo back to their ears

Refraction• Wave changes speed as it enters a second medium, causing

the wave to bend.

Absorption• Some sound is absorbed and reduced when hitting another

surface of passing through another medium• Types of surface for best absorption: draperies, cloth, etc.• Sound-absorbing materials are porous; sound waves entering

the tiny air-filled spaces bounce around until their energy is spent.

Diffraction• When a wave passes a barrier or moves through a hole in a

barrier it bends and spreads out.

• Example: We can hear people talking in the hall, even though we can’t see them.

Wave Speed• Waves in different mediums travel at different speeds. However, in

a given medium and under the same conditions the speed of the wave is constant

• The speed, wavelength, and frequency of a wave are related to each other by a mathematical formula.

• Speed = wavelength x frequency• Frequency = speed/wavelength• Wavelength = speed/frequency

OQ 10/2/13

•What does the speed of the wave mostly depend on?