Many of you will often want to talk to your neighbor while I'm lecturing. As long as it's on-topic and OK with your neighbor, it's OK with me. However, you have to be careful to not distract the people around you (or me - sound really carries in the classroom). That means you need to whisper. What's the difference between whispering and talking quietly?
Whispering is unvoiced. This means that the vocal chords in your throat don't vibrate. Rather than a loud sound coming from your vocal chords, a much quieter sound comes from the back of your mouth, at the top of your throat, and makes a "whispy", breathy, or hissing sound. It lacks the buzzy sound of normal speaking.
One way to learn whispering is to talk like your sighing. A sigh is unvoiced, just like a whisper. Gasping and panting are other types of unvoiced vocalizations.
Here is a resource on whispering: http://en.wikipedia.org/wiki/Whispering. It includes a short audio clip demonstrating what whispering sounds like.
Thanks for whispering!