Default [Q] help!! nexus 4 low mic volume during phone call,

Guys I need help in fixing my inbuilt mic. Volume is very low and friends on other side are unable to listen anything. Though it is working when I use Skype, viber or recording.

This happens few days after upgrading to KitKat and didn't solved after 4.4.2 upgrade. Let me know how to fix this.
Thanks in advance!!