[HOW TO] Disable noise reduction! No root!!
Ok, it seems people here are more interested in modifying their OS more than trying to understand it. Since JB 4.1.2 Galaxy S2 natively supports the disabling of the Noise Reduction system inbuilt to the device.
1. Reduced Battery usage on "Voice Calls"
2. Less call breakup in low signal areas
3. Sharper voice during calls.
4. Improvement of voice level for devices inside cases
Noted Issue in the OS
Because the option to disable the feature was implemented at a later time the system runs noise suppression even though the menu check box clearly says it is not suppose to. This is a temporary issue which can be fixed by Enabling and then disabling the option in the menu
1. Dialer Screen -> Menu Key -> Call Settings -> Additional Settings -> Check Noise reduction (Yes Enable it) -> Make a call
2. Dialer Screen -> Menu Key -> Call Settings -> Additional Settings -> Uncheck Noise reduction -> Make a call (Notice that noise reduction is now disabled)
Enjoy your Galaxy S2