iphone 5 volume on calls very low

Loads of people are reporting low volume through the iPhone 5 handset (when holding up to the ear).

An no, there is no film over the speaker !! Image may be NSFW.
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When someone calls, the sound is muffled, sounds like a very low bit-rate call. All the volumes are up as high as they go, and i can take the call in a quiet room and it sounds the same (so not the noise-cancelling part).

help, this is most annoying.