Having the same problem here. After some software update 3 weeks ago, the mic is not working more than 10% on this apps. It should be a software issue, but its quite strange that nobody is reffering to this problem, since it looks so widely spread...
Tried many things but no solution. I guess its software based, because in Lumia camera, video has good audio recording, but the rest is not working. Weird thing is that the phone calls mic works perfectly, there should be a way to asign that primary mic for skype, onenote, voice recording, etc (speaker mode mic)...
Hope we can contact Gabe Aul or somebody else related to notice this issue to MS...