There may be a bug impacting iOS 8 where the mail sound appears to be playing the tone twice, overlapping so it sounds like an echo. Original thread here: http://forums.macrumors.com/showthread.php?t=1786228 For those experiencing this, are you using a custom tone (i.e. created or purchased) or one of the iOS stock tones? Also, what device(s) are you experiencing this on? I'm using a custom tone that I made and it's happening on my iP6+. I have notifications off on my iPad mini so I haven't noticed on there. ***UPDATE** IT APPEARS THAT 8.0.2 HAS NOT FIXED THIS ISSUE.