I've read on other forums that the noise canceling microphone which is next to the headphone socket is supposed to reduce unwanted noise such as traffic etc, unfortunately because its so sensitive it also picks up your voice when speaking and can produce a rather nasty echo to the person on the other end of your call.This seems to be quite a problem for some people,having a case on the phone seems to make it worse,a few people have put a piece of tape over the mic and this seemed to cure it but not for everyone.As far as I know there is no way to turn the noise canceling off either as it's built into the hardware of the phone and there isnt any software settings to adjust it.
