It sounds different because it is different. "When you speak, the vocal folds in your throat vibrate, which causes your skin, skull and oral cavities to also vibrate, and we perceive this as sound," explains Ben Hornsby, a professor of audiology at Vanderbilt University. The vibrations mix with the sound waves traveling from your mouth to your eardrum, giving your voice a quality—generally a deeper, more dignified sound—that no one else hears.
Through a loudspeaker or recording device, you pick up sound only through air conduction. "The sound we're used to hearing has a lower frequency from the bone vibrations," Hornsby says. "We like that because it sounds rich and full." Many people cringe at the playback sound because our brain struggles to accept that this foreign voice is our own.
For the rest of the story: http://www.popsci.com/scitech/article/2009-06/why-your-voice-sounds-different-recordings?src=SOC&dom=tw