Sound and Music - Mission SM1 Detailed Help

Sammy is talking to Sally. Position A is a position in front of Sammy's mouth. Position B is a position in front of Sally's ear. In order for Sally to hear Sammy's voice, air particles must ____.


 
Propagation of Sound Waves:
Sound waves move (propagate) through a medium by means of particle-to-particle interaction. The source disturbs the immediately surrounding particles, causing them to vibrate about their fixed position at the same frequency as the source. These particles in turn force their nearest neighbors to vibrate about their fixed position which in turn forces their nearest neighbors to vibrate about their fixed position which in turn ... . As a result of this particle-to-particle interaction, a sound wave travels through the medium from one location to another.


 
A common misconception (wrong idea) regarding waves is that a wave involves the movement of matter from the source to other parts of a medium. In the case of a sound wave traveling through air, a student might believe that particles of air move at high speeds from the speaker to the hearer. But don't be fooled! Waves involve the transport of energy, not the transport of matter. When a sound wave travels through air, particles of air simply undergo a back-and-forth vibratory cycle about a fixed position. The air particles do not actually move from the speaker to the observer; they simply vibrate. Their vibrations force their nearest neighbors to vibrate which forces their nearest neighbors to vibrate which forces their nearest neighbors to vibrate.