I can hear it. Dean's voice hissing a short "s" and "AYUM" being how he pronounces the end. Sam would get louder at the end of Dean's name; "DeEAN" the "e" starts a little quieter but gets louder at the end of Dean's name.
Supernatural subtitles :"D - oh man, seriously these are hilarious! I need to start watching with subtitles. -[Dean randomly dies in shower] is the funniest subtitle in the history of Supernatural subtitles