As well as diagetic audio I am also adding sound effect to heighten the sense of drama. A few websites were recommended to me as great sources for royalty free sound effects and some I have used in the past. I found many useful effects for my project. I explored some websites that did not offer free sound effects, but I used the previews for research to get an idea of what sounds I needed and then looked for free alternatives
Some of the websites I used for research and/or downloading sounds:
http://www.soundsnap.com/
http://soundbible.com/
http://www.soundjay.com/
http://www.pacdv.com/sounds/index.html
http://free-loops.com/
http://www.mediacollege.com/downloads/sound-effects/
http://www.flashkit.com/soundfx/
