Mic external noise rejection different with the Plus
The 5S was excellent at rejecting ambient noise. Now that our mouth is so far from the microphone on the plus, Apple has to increase the mic pickup distance. I was able to hear the person next to the caller which never happened before. Previously you couldn't hear someone talking next to the caller.
This isn't a bug, there is no other way to do it. Just be aware that it is a new characteristic of this phone. Are others experiencing the same?