Just a quick post to hopefully help those out there who have just updated to the latest ICS(Android 4.0.4 at the time of writing), and have a Sony Xperia S mobile phone.
After updating from Gingerbread(2.3.3) to Android ICS (4.0.4) on your Sony Xperia S, you loose in call volume. When making/receiving phone calls, you can’t hear anyone on the other end.
Plug in a set of earphones/headphones. Now unplug it. Problem solved!
For some bizarre and ridiculous reason if you open the LiveWare Manager application on the phone, after the update has occurred, you’ll notice that the Headphones item has a little green dot next to it indicating that headphones mode is activated, hence why you can hear sweet nothing when making/receiving calls.
The above solution worked for me, I hope it manages to help others out there frustrated by the same thing.