The Nature of Sound

1. The Nature of Sound EQ: How do I define, describe and identify sound?

2. 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

3. 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?

4. 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 people’s ears and your own as well EQ: How do I define, describe and identify sound?

5. 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?

6. EQ: How do I define, describe and identify sound? Sound in Space 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. -

7. 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?

8. 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?

9. 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?

10. 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?

11. 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.

12. 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