1. The Nature of Sound

2. Sound is Longitudinal  Longitudinal wave or compression wave  Compression vs. rarefaction  Longitudinal wave or compression wave  Compression vs. rarefaction

3. How Sound is Produced  A vibration from a source (say a guitar string) sets the air molecules in motion  In some areas the air is compressed  And some areas it is spread out (rarefaction)  A vibration from a source (say a guitar string) sets the air molecules in motion  In some areas the air is compressed  And some areas it is spread out (rarefaction)

4. Sensing Pitch  The frequency of a sound wave is also known as pitch  Humans can sense sound waves with frequencies from 20 Hz to 20,0000 Hz  We hear sound because the vibrating air makes our ear drum vibrate and it sends signals to our brain.  The frequency of a sound wave is also known as pitch  Humans can sense sound waves with frequencies from 20 Hz to 20,0000 Hz  We hear sound because the vibrating air makes our ear drum vibrate and it sends signals to our brain.

5. Resonance  Drop a wrench and it clangs  The sound it makes is at its natural frequency  Resonance occurs when an object is forced to vibrate at its natural frequency.  Drop a wrench and it clangs  The sound it makes is at its natural frequency  Resonance occurs when an object is forced to vibrate at its natural frequency.

6. Tacoma Narrows Bridge