I'm having a very funky issue with whatsapp. Every time I open it I can clearly hear some white-noise coming out through the loudspeaker. Same happens with headphones. Since I am already experiencing heavy battery drain this is an even additional burden :/ Blergh. I'm with a Lumia 620 win 8.1 gdr1 phone.
It's a known bug sadly and Whatsapp don't appear to be in a hurry to fix it. When you first run it under 8.1 it tells you "some features may not work properly", or something like that.
Problem isn't there under 8.0, but instead you very rarely get notifications and nearly every time you open the app you are told "there has been a problem with notificaions, please restart your phone". Which, I might add, makes no difference whatsoever.