Listed below are some links that help describe what we will talking about on Wednesday July 6
The first article is
Other links below may help give a bit more information.
Electricity: http://science.howstuffworks.com/electricity5.htm
Speakers: http://electronics.howstuffworks.com/speaker.htm
Types of microphones: http://electronics.howstuffworks.com/search.php?terms=microphones
Amplifier Overview http://www.howstuffworks.com/amplifier.htm