# 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.

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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.

Sound is a form of energy that travels in waves.
What is SOUND? Pg 25 Sound 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: /30/ 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 here Lower 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)

REFLECTION Bouncing back of a wave after hitting a barrier
Sound 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 /2/13 What does the speed of the wave mostly depend on?

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