# If a tree falls in a forest, and no one is around to hear it, did it make a sound?

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If a tree falls in a forest, and no one is around to hear it, did it make a sound?

What is sound? Sound is a form of energy, just like electricity and light. Sound is made when air molecules vibrate and move in a pattern called waves or sound waves.

Think of when you clap your hands, or when you slam the car door shut. That action produces sound waves, which travel to your ears and then to your brain, which says, "I recognize that sound."

Sound is created by vibrations that produce waves of energy that move through matter

Vibration: a back and forth movement (that causes sound)

*ALL sound is caused by vibration!

The vibrations travel in waves away from the object. Sound Wave: a longitudinal wave caused by vibrations traveling through a medium.

Sound Waves are longitudinal (compressional) waves. The molecules are being pressed together as the sound waves move through matter. Longitudinal waves travel through the springs just like sound waves travel through the air.

Compression: the part of a sound wave where the molecules are crowded together Rarefraction: the part of a sound wave where the molecules are spread apart

Medium- a substance through which a wave can travel.

Properties of Sound

Pitch Pitch = how high or low a sound is

Properties of Sound frequency Pitch depends on frequency

Remember that Frequency is… the number of waves that pass by a point each second

Properties of Sound Larger frequency = higher pitch Smaller frequency = lower pitch slinky demo

Notice the amplitude (volume)is the same, but the pitch changes. Low frequency Low Pitch Medium frequency Medium Pitch High frequency High Pitch how do you think opera singers can break glass when hitting high notes?

Pitch that “Hertz” hertz Pitch is measured in hertz (Hz)

Humans can hear sounds that vibrate between 20 times a second (20 Hertz) to about 20,000 times a second (20,000 Hertz).

Ultrasonic: a sound that is HIGHER than 20,000 Hz

Examples:

Ultrasonic: a sound that is HIGHER than 20,000 Hz Examples: Bats Dogs Dolphins

Infrasonic: a sound that is LOWER than 20 Hz

Infrasonic: a sound that is LOWER than 20 Hz Examples: ElephantsWhales

http://ww w.youtube. com/watch ?v=AXhR mv1mrs4 Can you hear this? short clip http://www.yout ube.com/watch? v=VxcbppCX6Rk http://www.you tube.com/watch ?v=H- iCZElJ8m0 Can you hear this? medium length clip Can you hear this? longest clip

Properties of Sound Loudness Loudness measures how well a sound can be heard.

Properties of Sound Loudness depends on amplitude

Remember that Amplitude is… the wave height

Properties of Sound lower amplitude = softer sound higher amplitude = louder sound

Loud sound =

Soft sound =

LOUDNESS! decibels Loudness is measured in decibels

*Pain threshold for hearing is 120 dB (hearing loss can occur)

Pitch Frequency Hertz Loudness Amplitude Decibels can you think of a fun acronym for remember ing these?

Sound Travel

How does sound travel differ through different states of matter?

Sound travels through all forms of matter.

Speed of Sound The speed of sound depends on the medium it travels through.

Why does sound travel fastest in a solid?

Solid- molecules are packed tightly Examples: rock, metal, wood Solid =

Liquid- molecules are close together Example: water Liquid =

Gas- molecules spread apart Example: air Gas =

Sound travels fastest through solids because the molecules are tightly packed together

Sound travels fastest through solids

Vacuum: a place where there are NO molecules (outer space) *There is no sound in outer space because there are no molecules (there is NO matter)

Sound Waves Videos Gaggle video: “Julian Treasure: The 4 ways sound affects us” (4:27) http://www.youtube.com/watch?v=-gya8fRY4KQ “The coolest things sounds waves do” (2:59) http://www.youtube.com/watch?v=Ude8pPjawKI

A tiny piece of space junk hits this space shuttle. There are two astronauts in the picture – one inside the capsule, and one outside. Can either of them hear the impact? What do you think?

Summarizer Number 1-4 on your paper. Discuss the pitch and loudness of each wave. Pitch = high or lowLoudness= soft or loud

pitch.

“The Sound of Vomit” on discovery education (21:51) https://app.discoveryeducation.com/search?Ntt=the+so und+of+vomit first 5 minutes answers Activator Properties of Sound Video

The Doppler Effect Doppler Effect: The change in pitch (frequency) as a sound gets closer to you.

*The ______a sound gets, the _______the pitch. *The __________ a sound gets, the _______the pitch. closer higher further away lower

Draw this now!...

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