1. I NTRODUCTION TO SOUND

2. S OUND IS EVERYWHERE Imagine you are taking a walk through a park on a hot, summer day. With a partner, brainstorm all of the different sounds you are likely to hear on your walk

3. W HAT I S S OUND ? Sound is created by vibrations A vibration is the complete back-and-forth motion of an object Sound waves travel as longitudinal waves

4. S OUND W AVES R EQUIRE A M EDIUM Sound is transmitted through the vibrations and collisions of particles of matter (example: air particles). Because of this, sound waves require a medium. A medium is a substance through which a wave can travel Using what you know about wave speed, discuss with a partner whether a sound wave would travel fastest through a solid (ex: a desk), a liquid (ex: water), or a gas (ex: air) and why. ??

5. PROPERTIES OF SOUND : SPEED The speed of sound depends on the medium Sound travels fastest through solids because the particles in solids are close together. Sound travels slowest through gases because the particles in gases are spread out. The speed of sound also depends on temperature In general, the cooler the medium, the slower the speed of sound because particles in cool materials move slower than particles in warm materials, so they transmit energy more slowly

6. PROPERTIES OF SOUND : PITCH How low or high you perceive a sound to be is the pitch of that sound The pitch of a sound depends on the frequency of the sound wave High Frequency = High Pitch Low Frequency = Low Pitch

7. PROPERTIES OF SOUND : LOUDNESS Loudness is how loud or soft a sound is perceived to be Demonstration: Start by lightly tapping the top of your desk with the palm of your hand. Now bang on the top of your desk with the palm of your hand What happened? What did you have to do to produce a louder sound?

8. PROPERTIES OF SOUND : LOUDNESS The harder you strike the desk, the louder the noise that is produced. As you strike the desk harder, you transfer more energy to the desk. The desk moves with a larger vibration and transfers more energy to the surrounding air. This increase in energy causes air particles to vibrate farther from their rest positions When you strike a desk, you are increasing the amplitude of the sound waves being created Larger Amplitude = Louder Sound Smaller Amplitude = Softer Sound