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

2. Sound A type of wave produced by a vibrating object. It travels through matter as a longitudinal wave. EQ: How do I define, describe and identify sound?

3. 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. wavelength compression rarefaction EQ: How do I define, describe and identify sound?

4. How do I 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 people’s 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, they transfer their energy to the air and make it move, too. EQ: How do I define, describe and identify sound?

7. Sound in Space Sound can only travel if a medium is present to transmit the waves. There are no air molecules in outer space,so there is nothing for the sound to travel through. Space is a vacuum(empty space). - EQ: How do I define, describe and identify sound?

8. The Speed of Sound Depends on 3 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 –Compare rubber band and modeling clay –Sound travels better in mediums that are more elastic because when the particles are compressed, they quickly spread out again –Which has the most elasticity: solid, liquid or gas? EQ: How do I define, describe and identify sound?

10. Density How much matter (mass) there is in a given space. The particles in a dense material travel slower than in a less dense material. Therefore, sound will move slower through more dense materials. EQ: How do I define, describe and identify sound?

11. Temperature Sound travels slower at low temperatures and faster at higher temperatures. Example -At 20 C, speed of sound in air is about 340m/s. At 0 C, the speed is 331m/s. EQ: How do I define, describe and identify sound?

12. Class Work and Homework Read pages O 40 – O 44, Answer questions 1- 4 on 0-44. (Pay special attention to figure 4, page 42) EQ: How do I define, describe and identify sound?