The Nature of Sound

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The Nature of Sound

• EQ How do I define, describe and identify sound?

2
Sound
EQ How do I define, describe and identify sound?
A type of wave that is produced by a vibrating
object and that travels through matter as a
longitudinal wave.
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Sound is a longitudinal wave that travels through
a material medium, such as air. In this case the
vibrating drum is causing the air particles to
vibrate.
EQ How do I define, describe and identify sound?
rarefaction
wavelength
compression
4
How do you make sound?

• You force air up through your voice box, or
  larynx
• Your larynx consists of two folds of tissue
  called vocal chords (like guitar strings)

EQ How do I define, describe and identify
sound?
5
How you speak .

• As the vocal chords move closer together, the air
  between them is compressed. As they move apart,
  the air spreads out, or rarefies. The air carries
  the longitudinal waves to other peoples ears and
  your own as well

EQ How do I define, describe and identify
sound?
6
Sound in Solids and Liquids

• Sound travels through solids and liquids
• Example- knocking on a door
• When you knock, the particles of the door vibrate
• The vibration creates sound waves that travel
  through the door
• When the sound waves reach the other side, the
  same vibrations make sounds waves in the air.

EQ How do I define, describe and identify
sound?
7
Sound in Space
EQ How do I define, describe and identify
sound?

• Sound can only travel if a medium is available to
  transmit the compressions and rarefactions. In
  outer space, there are no molecules so there is
  nothing for the sound to travel through and so
  there is no sound. Space is a vacuum-A space
  containing no particles of matter.
• -

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The Speed of Sound

• It depends on three properties of the medium it
  travels through
• Elasticity
• Density
• Temperature

EQ How do I define, describe and identify
sound?
9
Elasticity

• The ability of a material to bounce back to its
  original shape
• Solid materials are usually more elastic
• Sound travels better in mediums that have a high
  degree of elasticity because when the particles
  are compressed, they quickly spread out again
  increase speed of sound
• Which has the most elasticity, solid, liquid or
  gas?

EQ How do I define, describe and identify
sound?
10
Density

• How much matter, or mass, there is in a given
  space or volume
• The denser the medium, the more mass it has. The
  particles in a dense material travel slower than
  in a less denser material, therefore, sound will
  move slower through more dense materials.

EQ How do I define, describe and identify
sound?
11
Temperature

• In a given medium, sound travels slower at lower
  temperatures and faster at higher temperatures.
• At 20 C, speed of sound in air is about 340m/s,
  at 0 C the speed is 331m/s
• At higher altitude the air is colder, so sound
  travels slower at higher altitude

EQ How do I define, describe and identify
sound?
12
Moving Faster Than Sound

• October 14, 1947, Chuck Yeager broke the sound
  barrier
• October 15, 1997, Andy Green broke the speed of
  sound on the ground with his jet powered car
  called Thrust.

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Class Work and Homework
EQ How do I define, describe and identify
sound?

• Fill In
• What did I learn
• Confused
• Say
• Read pages O 40 O 44, Answer questions 1- 4 on
  0 44
• (Pay special attention to figure 4, page 42)
• 2-1, Worksheet answer all questions